Optical limiting action of C60 doped poly(dimethylacetylendicarboxylate)

The optical limiting action of poly(dimethylacetylendicarboxylate) polymer doped with fullerene C₆₀ has been investigated under irradiation with 10 ns laser pulses at 532 nm. The optical limiting measurements were performed at four different dopant concentrations. The threshold limiting fluence at 0.3 J/cm² was observed at high doping concentrations, with transmission of about 55%. An explanation based on the combination of two-photon absorption and reverse saturable absorption was proposed for its nonlinear optical absorption behavior.     

Synthesis and characterization of sulfur-containing polyacetylene derivative: Synthesis of poly(phenyl propargyl sulfide) and its electro-optical properties

Sulfur-containing conjugated polymer was synthesized by the polymerization of phenyl propargyl sulfide by transition metal catalysts such as PdCl₂, RuCl₃, (NBD)PdCl₂, WCl₆, and MoCl₅. The polymerization proceeded well in homogeneous manner to give a moderate yield of polymer. The chemical structure of poly(phenyl propargyl sulfide) was characterized by NMR (¹H–, ¹³C–), IR, and UV–visible spectroscopy, and elemental analysis to have the conjugated polymer backbone with the designed moieties. The FT-IR spectra of the polymer did not show the acetylenic CC bond stretching (2119 cm⁻¹) and acetylenic C–H bond stretching (3293 cm⁻¹) frequencies of the monomer. The thin polymer film exhibited reversible electrochemical behaviors between the doping and undoping peaks. Poly(phenyl propargyl sulfide) showed the characteristic UV–visible absorption band at 360 nm and blue PL spectrum at 460 nm, corresponding to the photon energy of 2.70 eV. The energy band gap of poly(PPS) was estimated to be 2.77 eV from the analysis of the absorption edge.     

Nonlinear optical properties of erbium doped zinc oxide (EZO) thin films

Undoped and Erbium (Er) doped zinc oxide (EZO) thin films were deposited on glass substrate by sol–gel method using spin coating technique with different doping concentration. EZO films were characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), UV–VIS-NIR transmission and single beam z scan method under illumination of frequency doubled Nd:YAG laser. The deposited films were found to be well crystallized with hexagonal wurtzite structure having a preferential growth orientation along the ZnO (002) plane. A blue-shift was observed in the band gap of EZO films with increasing Er concentration. All the films exhibited a negative value of nonlinear refractive index (n₂) at 532 nm which is attributed to the two photon absorption and weak free carrier absorption. Third order nonlinear optical susceptibility, χ⁽³⁾ values of EZO films were observed in the remarkable range of 10^? 6 esu. EZO (0.4 at.%) sample was found to be the best optical limiter with limiting threshold of 1.95 KJ/cm².     

Effect of Fe3+ doping on structural,optical and electrical properties δ-Bi2O3 thin films

Fe³⁺ doped δ-Bi₂O₃ thin films were prepared by sol–gel method on quartz glass substrate at room temperature and annealed at 800 °C. The thin films were then characterized for structural, surface morphological, optical and electrical properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption measurements and d.c. two-probe, respectively. The XRD analyses revealed the formation δ-Bi₂O₃ followed by a mixture of Bi₂₅FeO₄₀ and Bi₂Fe₄O₉. SEM images showed reduction in grain sizes after doping and the optical studies showed a direct band gap which reduced from 2.39 eV for pure δ-Bi₂O₃ to 1.9 eV for 10% Fe³⁺ doped δ-Bi₂O₃ thin film. The electrical conductivity measurement showed the films are semiconductors.     

Thermal stability and spectroscopic properties of erbium-doped niobic-tungsten–tellurite glasses for laser and amplifier devices

Er³⁺ doped niobic-tungsten–tellurite glasses doped with concentration of Er³⁺ ion up to 3 wt% were fabricated. The effect of Er³⁺ doping concentration on thermal stability and optical properties was investigated in order to obtain the most suitable rare earth content for developing 1.5 μm compact fiber amplifier pumped with a commercial telecom 980 nm laser diode. The maximum doping concentration allowed was found to be around 1.77×10²⁰ ions/cm³, for which a broad 1.5 μm emission spectra of 65 nm FWHM and a lifetime of 3.4 ms for the ⁴I_13/2 level was measured.     

Third order nonlinear optical properties of ethyltriphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate (III)

A novel organometallic compound, ethyltriphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate (III), abbreviated as TPEPADT, was synthesized. The TPEPADT doped poly(methyl methacrylate) (PMMA) thin film with a mass fraction of 1% (1 wt.%) was prepared by using a spin-coating method. The third-order nonlinear optical properties of TPEPADT in acetonitrile solution and TPEPADT-doped PMMA thin film were investigated by using the laser Z-scan technique at the wavelength 1064 nm with laser duration of 20 ps. The linear refractive index of the polymer thin film was also studied. The Z-scan curves revealed that both TPEPADT in acetonitrile solution and the polymer thin film possessed negative nonlinear refraction, exhibiting a self-defocusing effect and nonlinear absorption was negligible under the experimental conditions used. The nonlinear refractive index was calculated to be ?1.9 × 10^?18 m²/W for TPEPADT in acetonitrile solution and ?8.9 × 10^?15 m²/W for the polymer thin film. These results suggest that TPEPADT have potential for the application of all-optical switching devices.     

Optical characteristics of Tb-doped InBO3 nanocrystals

InBO₃ nanocrystals doped with Tb³⁺ ions are prepared via the sol–gel method. The structure, morphology, and optical properties of the nanocrystals are characterized by X-ray diffraction, high-resolution transmission electron microscopy, field-emission scanning electron microscopy, and photoluminescence analysis. The results show that a hexagonal InBO₃ phase forms at above 650 °C. A second phase of In₂O₃ begins to appear with Tb doping of over 3 mol%. The ⁵D₄→⁷F₅ (553 nm) transitions of Tb³⁺ ions in the InBO₃ host are observed at 2 mol%. The decay time of Tb-doped InBO₃ nanocrystals is about 2.1 ms. For Tb-doped InBO₃ nanocrystals excited at 237 nm and 553 nm wavelengths, the 2 mol% doping level yields the highest saturation of green emission. The emission shifts from green to yellow when the doping concentration is increased from 1 to6 mol%, due to the ⁵D₄→⁷F₅ transition.     

Incorporation of Ce3+ in crystalline Gd-silicate nanoclusters formed in silica

Structural and optical properties of sol–gel silica based glassceramics doped with 0.1 mol% Ce and codoped with Gd at high concentrations, from 5 mol% up to 40 mol%, are investigated and compared to those of analogous samples doped only with Ce. Raman scattering, transmission electron microscopy, and x-ray diffraction reveal the formation of Gd apatite-like silicate (Gd_4.67O(SiO₄)₃) and of Gd pyrosilicate (Gd₂Si₂O₇) nanophases whose morphology and crystallinity depend on the Gd concentration and thermal treatments. Optical absorption measurements demonstrate the role of the densification atmosphere in modifying the charge state of Ce ions. The incorporation of Ce³⁺ ions in the nanophases is put in evidence by photo- and radio-luminescence results.     

Conductivity and optical studies of plasticized solid polymer electrolytes doped with carbon nanotube

Solid polymer electrolyte films based on Poly(ethylene oxide) (PEO) complexed with lithium hexafluorophosphate (LiPF₆), ethylene carbonate (EC) and amorphous carbon nanotube (αCNTs) were prepared by the solution cast technique. The conductivity increases from 10^?10 to 10^?5 Scm^?1 upon the addition of salt. The incorporation of EC and αCNTs to the salted polymer enhances the conductivity significantly to 10^?4 and 10^?3 Scm^?1. The complexation of doping materials with polymer were confirmed by X-ray diffraction and infrared studies. Optical properties like direct band gap and indirect band gap were investigated for pure and doped polymer films in the wavelength range 200–400 nm. It was found that the energy gaps and band edge values shifted to lower energies on doping.     

UV–Vis and NMR spectroscopic investigations on effective and selective non-covalent interactions between fullerenes and calix[6]arene

Ground state non-covalent interactions between a macro cyclic calixarene receptor, namely, 4-tert-butylcalix[6]arene (1), and fullerenes (C₆₀ and C₇₀) were studied in toluene medium by absorption spectrophotometric method. Absorption band due to the charge transfer (CT) transition have been observed in the visible region between fullerenes and 1. Utilizing the CT absorption bands, various important physicochemical parameters like oscillator strength, resonance energy, transition dipole strength of the fullerene-1 complexes and ionization potential of 1 is determined in present investigations. From Jobs method of continuous variation, it is observed that both C₆₀ and C₇₀ form stable 1:1 complexes with 1. The most fascinating feature of the present study is that 1 binds selectively C₇₀ compared to C₆₀ as obtained from binding constant (K) data of C₆₀–1 (K_C60–1) and C₇₀–1 (K_C70–1) complexes, i.e., K_C60–1 = 32,400 dm³·mol^? 1 and K_C70–1 = 110,000 dm³.mol^? 1 and selectivity (K_C70–1/K_C60–1) = 3.4. ¹H NMR analysis provides very good support in favor of strong binding between C₇₀ and 1.     

Study of EVOH based single ion polymer electrolyte: Composition and microstructure effects on the proton conductivity

A comb-like EVOH based single ion polymer electrolyte (EVOH-g-SPEG) was synthesized by sulfonification of EVOH grafts 2-(2-chloroethoxy) ethanol (C₄H₉O₂Cl)/2-[2-(2-chloroethxy) ethoxy] ethanol (C₆H₁₃O₃Cl) with 1, 3-propane sultone. The main chain of the comb-like polymer is hydrophobic polyethylene segments; the side chain is hydrophilic poly (ethylene glycol) (PEG) segment, which can solubilize large amounts of inorganic salts. The sulfonic acid group was introduced onto the end of the PEG side chain. The acid form of SPE was successfully obtained by being dialyzed from the products with acid solution. The saturation water sorption of EVOH-g-SPEG membrane increased with the side chain length and the immersion time. The XRD results indicate that the water in SPE membrane region can destroy the membrane crystalline structure and the water absorption membranes are nearly amorphous. AFM phase images of the hydration membranes clearly show the hydrophilic domains, with sizes increasing from 10 to 35 nm as a function of the side chain length. A phase inversion could be observed when n ≥ 5, which was consistent with a rapid increase in water absorption. And the ion conductivity is also measured by AC impedance. The conductivity is greatly influenced by ion exchange capacity and water sorption. The comb-like EVOH-g-SPEG polymer electrolyte grafts with 2 PEG side chain provides the highest ionic conductivity (1.65 × 10^− 3 S cm^− 1). The comb-like polymer could be a candidate as new polymeric electrolyte material for fuel cells and other electrochemical devices.     

Absorption,luminescence, and electron paramagnetic resonance of molybdenum ions in CdWO4

A single crystal of cadmium tungstate (CdWO₄) containing approximately 200 ppm of molybdenum was grown by the Czochralski method and then characterized in a series of optical absorption, photoluminescence (PL), photoluminescence excitation (PLE), and electron paramagnetic resonance (EPR) experiments. The Mo⁶⁺ ions substitute for W⁶⁺ ions and serve as recombination sites for electrons and holes when the crystal is exposed to ionizing radiation. A charge-transfer absorption band for the Mo⁶⁺ ions was observed near 320 nm at 10 K. The PL experiments, performed at low temperature with 325 nm excitation, showed a Mo-associated emission peaking near 680 nm. A direct correlation of the 680 nm emission and the 320 nm absorption band was established by the PLE data. When these doped CdWO₄ crystals are exposed at low temperature either to light that is near or above the band gap or to X-rays, the Mo⁶⁺ ions can trap an electron and form stable Mo⁵⁺ ions. The EPR spectrum of the Mo⁵⁺ ions was observed at temperatures near 15 K, and a complete set of parameters describing the g matrix was obtained from an angular dependence study.     

Preparation and photocatalytic degradation of erbium doped titanium dioxide nanorods

Photocatalytic degradation of methylene blue (MB) in water was examined using Er³⁺-doped TiO₂ (Er–TiO₂) nanorods prepared by a sol–gel derived electrospinning, calcination, and subsequent mechanical grinding. Different concentrations of Er dopant in the range of 0–1.0 mol% were synthesized to evaluate the effect of Er content on the photocatalytic activity of TiO₂. Among Er³⁺–TiO₂ catalysts, the 0.7 mol% Er³⁺–TiO₂ catalyst showed the highest MB degradation rate. The degradation kinetic constant (k) increased from 1.0 × 10^?3 min^?1 to 5.1 × 10^?3 min^?1 with the increase of Er³⁺ doping from 0 to 0.7 mol%, but decreased down to 2.1 × 10^?3 min^?1 when Er³⁺ content was 1.0 mol%. It can be concluded that the degradation of MB under UV radiation was more efficient with Er³⁺–TiO₂ catalyst than with pure TiO₂. The higher activity might be attributed to the transition of 4f electrons of Er³⁺ and red shifts of the optical absorption edge of TiO₂ by erbium ion doping.     

Growth and characterization of pure and doped bis thiourea zinc acetate: Semiorganic nonlinear optical single crystals

Metal–organic coordination complex single crystals bis thiourea zinc acetate (BTZA) and Cd²⁺ doped BTZA have been synthesized and grown successfully by slow-cooling technique from their aqueous solutions. Single crystals of pure and Cd²⁺ doped BTZA with dimensions of 35 × 4 × 2 mm³ and 10 × 5 × 6 mm³, respectively were obtained with well defined morphology. The as grown single crystals are characterized by single crystal XRD studies and melting point measurements which reveal the incorporation of metallic dopants has not changed the structure of the parent crystal. The powder X-ray diffractogram of the grown crystals has been recorded and the various planes of reflection identified shows shift in the peak positions. The metal coordination with thiourea through sulphur in pure and Cd²⁺ doped BTZA were ascertained by FTIR studies and optical absorption study to identify the UV cut-off range. The presence of metals in pure and Cd²⁺ doped BTZA crystal lattice were confirmed by atomic absorption spectroscopy (AAS). The thermal decomposition of pure and Cd²⁺ doped BTZA crystals were investigated by thermo gravimetric analyses (TGA) and differential thermal analysis (DTA) indicate that doped crystals are more stable than pure crystals. The dielectric response of the crystals were studied in the frequency range 100 Hz–5 MHz at different temperatures and the results are discussed. Second harmonic generation (SHG) measurement confirms that the pure and Cd²⁺ doped BTZA have nonlinear optical (NLO) property. Laser damage threshold value of 12.44 MW/cm² has been determined using Q-switched Nd:YAG laser operating at 1064 nm and with 8 ns pulses in single shot mode for pure BTZA single crystal is reported for the first time.     

Luminescence characteristics of cobalt doped TiO2 nanoparticles

TiO₂ nanoparticles doped with two different concentrations of Cobalt, 0.02 and 0.04 mol, are prepared by sol–gel method. The crystalline phase of the doped and undoped nanoparticles and particle sizes are observed with X-ray diffraction and transmission electron microscope. FTIR confirms the bonding interaction of Co²⁺ in TiO₂ lattice framework. The UV absorption spectra of the doped material shows two absorption peaks in the visible region related to d–d electronic transitions of Co²⁺ in TiO₂ lattice. Compared to undoped TiO₂ nanoparticles, the cobalt doped samples show a red shift in the band gap. Steady state photoluminescence spectra give emission peaks related to oxygen defects. The decrease in the intensity ratio of UV/visible emission peaks confirms distortion of structural regularity and formation of defects after doping. The intensity ratio of different visible emission peaks is nearly same for undoped and 0.02 Co²⁺. However, this ratio decreases profoundly at 0.04 Co²⁺, due to concentration quenching effect. Photoluminescence excitation spectra, recorded at 598 nm emission wavelength, give different excitation peaks associated with oxygen vacancies and Co²⁺. Time resolved photoluminescence spectra give longer decay time for doped samples, indicating longer relaxation of conduction band electrons on the defect and on dopant sites.     

Nonlinear optical properties of silver colloidal solution by in situ synthesis technique

The silver colloidal solutions were prepared by in situ synthesis technique in the presence of the Polymethyl Methacrylate, which was polymerized by reversible addition-fragmentation transfer. The UV–VIS spectra and transmission electron microscopy had shown the formation of sphere silver nanoparticles with average size of 10 nm. Nonlinear optical properties as a function of silver concentration were studied using Z-scan technique with 13 ns pulse duration at 532 nm. The optical nonlinearity enhancement was observed by increasing the concentration. The third-order nonlinear susceptibility χ⁽³⁾ was measured to 1.045 × 10⁻¹¹ esu when the concentration was 2.13 mg/ml. Besides, the sample was founded to exhibit a shift from saturable absorption to reverse saturable absorption at higher incident laser energy. The reverse saturable absorption was observed to be responsible for the optical limiting characteristics in our experiments.     

Synthesis and growth of sodium bitartrate monohydrate a new organometallic nonlinear optical single crystal

Sodium bitartrate monohydrate (SBTMH) a new organometallic nonlinear optical material, with molecular formula, [C₄H₅NaO₆ · H₂O] has been synthesized at ambient temperature. Spectral, thermal and optical techniques have been employed to characterize the new material. Bulk single crystals of size 13 × 4 × 4 mm³ of SBTMH have been grown by slow cooling method. The unit cell parameters of the grown crystal were determined by single crystal XRD. Functional groups present in the sample were identified by FTIR spectral analysis. Thermal stability of SBTMH was determined using TGA/DTA. The grown crystals exhibit nonlinear properties. The dielectric response of the crystal with varying frequencies was studied. The optical transparency range and the lower cut-off wavelength of the material were identified from the UV–vis–NIR absorption spectrum.     

Superior performance characteristics for the poly(2,5-dimethoxyaniline)–poly(styrene sulfonic acid)-based electrochromic device

We have fabricated an electrochromic (EC) device with poly(2,5-dimethoxyaniline), PDMA, entrapped in poly(styrene sulfonic acid) (PSS) as an electrochromic layer. The device showed improved performances like stability, optical contrast, etc., over the device with a PDMA layer doped by H₂SO₄. In the process of fabrication of the EC device with a sandwich configuration, indium tin oxide (ITO)/PDMA–PSS||poly(ethyleneimine) (PEI)/orthophosphoric acid (H₃PO₄)/WO₃/ITO, electrochemical polymerization of 2,5-dimethoxyaniline (DMA) was performed with PSS as electrolyte and ITO coated glass as working electrode. The performance characteristics of EC device, like optical contrast, stability, switching time, etc., were followed by cyclic voltammetry, double potential step chronoamperometry and in-situ spectroelectrochemistry. The device was operated in between − 1 V and + 1 V, and absorption characteristics were followed by in-situ UV–visible spectroscopy. A visible contrast in color upon switching the potential from − 1 V to + 1 V was noticed for the device. The device was pale yellow at − 1 V and dark green at + 1 V. Incorporation of PSS into PDMA resulted enhancement in the performance of the complementary electrochromic device. The optical contrast of the device was improved by incorporating PSS into PDMA matrix. The device retained nearly 50% of their optical contrast after 10,000 double steps informing the superior performance of PDMA–PSS in the EC device.     

Spectroscopic properties of Co2+: ZnAl2O4 nanocrystals in sol–gel derived glass–ceramics

Transparent glass–ceramics containing zinc–aluminum spinel (ZnAl₂O₄) nanocrystals doped with tetrahedrally coordinated Co²⁺ ions were obtained by the sol–gel method for the first time. The gels of composition SiO₂–Al₂O₃–ZnO–CoO were prepared at room temperature and heat-treated at temperature ranging 800–950 °C. When the gel samples were heated up to 900 °C, ZnAl₂O₄ nanocrystals were precipitated. Co²⁺ ions were located in tetrahedral sites in ZnAl₂O₄ nanocrystals. X-ray diffraction analysis shows that the crystallite sizes of ZnAl₂O₄ crystal become large with the heat-treatment temperature and time, and the crystallite diameter is in the range of 10–15 nm. The dependence of the absorption and emission spectra of the samples on heat-treatment temperature were presented. The difference in the luminescence between Co²⁺ doped glass–ceramic and Co²⁺ doped bulk crystal was analysed. The crystal field parameter D_q of 423 cm⁻¹ and the Racah parameters B of 773 cm⁻¹ and C of 3478.5 cm⁻¹ were calculated for tetrahedral Co²⁺ ions.     

Infrared spectroscopic and conductivity studies of poly(N-methylpropylenimine)/lithium triflate electrolytes

Poly(propylenimine), PPI, was methylated using Eschweiler-Clark conditions to produce poly(N-methylpropylenimine), PMPI. Differences may be seen in the IR spectra of the PMPI (–CH₂CH₂CH₂NCH₃–) and its homolog poly(N-methylethylenimine), PMEI, (–CH₂CH₂NCH₃–), especially in the conformation region (~ 1100 to ~ 1400 cm^− 1). The addition of lithium trifluoromethanesulfonate, (LiCF₃SO₃), sharpens the distinctions between these systems. Comparison of IR spectra of polymer:LiCF₃SO₃ complexes at compositions ranging from pure polymer to 5:1 N:Li⁺ (molar ratio) suggests significant differences in the nature of polymer salt interactions and the complex structure present in each system. These are further evidenced by differential scanning calorimetry data in which PMPI displays less variation in glass transition temperature, T_g, with the addition of salt than seen in PMEI. These observations may be interpreted in terms of local structural changes originating in cation–anion and cation–polymer interactions, particularly at mid to high salt concentrations.