Preparation and nonlinear optical properties of Au nanoparticles doped TiO2 thin films

Nano-sized noble metal nanoparticles doped dielectric composite films with large third-order nonlinear susceptibility due to the confinement and the enhancement of local field were considered to be applied for optical information processing devices, such as optical switch or all optical logical gates. In this paper, sol–gel titania thin films doped with gold nanoparticles (AuNPs, ~10 nm in average size) were prepared. AuNPs were firstly synthesized from HAuCl₄ in aqueous solution at ~60 °C, using trisodium citrate as the reducing agent, polyvinylpyrrolidone as the stable agent; then the particle size and optical absorption spectra of the AuNPs in aqueous solutions were characterized by transmitting electron microscopy and UV–Vis–NIR spectrometry. Sol–gel 2AuNPs–100TiO₂ (in %mol) thin films (5 layers, ~1 μm in thickness) were deposited on silica glass slides by multilayer dip-coating. After heat-treated at 300–1,000 °C in air, the AuNPs–TiO₂ thin films were investigated by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The nonlinear optical properties of the AuNPs–TiO₂ thin films were measured with the Z-scan technique, using a femtosecond laser (200 fs) at the wavelength of 800 nm. The third-order nonlinear refractive index and nonlinear absorption coefficient of 2AuNPs–100TiO₂ films were at the order of 10^?12 cm²/W, and the order of 10^?6 cm/W, respectively, and the third-order optical nonlinear susceptibility χ⁽³⁾ was ~6.88 × 10^?10 esu.     

Diode effect caused by sequence of benzothiazole on optical properties

In this work, two kinds of benzothiazole derivatives were synthesized. The third-order nonlinear optical properties of the benzothiazole derivatives in minimal curative dose (DCM) were analyzed using the Z-scan measurement at 532 nm with a 120 fs pulse laser. The largest third-order nonlinear susceptibility (χ⁽³⁾) and second-order hyperpolarizability of the complexes (γ) were estimated at 1.4 × 10^?13 esu and 0.86 × 10^?30 esu, respectively. The results showed that the sequence of 2- and 6-position in benzothiazole has served as a “diode,” linking to the other groups that had great influence on the optical properties such as fluorescence and nonlinear optical absorption, and the increase of the polarity and the extension of the conjugate structure had benefits to the third-order nonlinearity. The experimental findings were confirmed with the use of DFT, TDDFT, and ZINDO calculations.     

Synthesis,crystal structure,and third-order non-linear optical properties of a new Cd(II) polymer constructed from pyrazine-2-carboxylic acid

A new cadmium(II) pyrazine-2-carboxylate coordination polymer, {[Cd(L)(H₂O)₂(SO₄)_0.5]₂·H₂O}_n (1) (HL = pyrazine-2-carboxylic acid), has been synthesized by low-temperature solid-state reaction. Single-crystal X-ray analyses reveal that 1 possesses a 3-D framework structure. The polymer 1 was characterized by elemental analyses, thermogravimetric analyses, X-ray powder diffraction analyses, IR spectra, and UV–visible spectra. The third-order non-linear optical properties were also investigated and they exhibit nice non-linear absorption and self-defocusing performance with modulus of the hyperpolarizability (γ) 1.30 × 10^?30 esu for 1 in a 2.01 × 10^?4 M?dm^?3 DMF solution.     

Study of Linear and Nonlinear Optical Properties of Four Derivatives of Substituted Aryl Hydrazones of 1,8‐Naphthalimide

Four 1,8‐naphthalimide hydrazone molecules with different electron‐donating groups have been applied in the study of linear and nonlinear optical (NLO) properties. These compounds showed strong green emission in solution. Their NLO properties such as two‐photon absorption (TPA) behavior with femtosecond laser pulses ca. 800 nm and excited‐state absorption (ESA) behavior with nanosecond laser pulses at 532 nm were investigated. Compound 4 presented the largest two‐photon cross section (550 GM) among them due to two factors: the conjugated length of compound 4 is the longest and the electron‐donating ability of compound 4 is the strongest. Different from TPA behavior, compound 2 showed the best nonlinear absorption properties at 532 nm and its nonlinear absorption coefficient and third‐order nonlinear optical susceptibilities χ ⁽³⁾ were up to 1.41×10^?10 MKS and 4.65×10^?12 esu, respectively. Through the modification of the structure, the nonlinear optical properties of these compounds at different wavelengths (532 and 800 nm) were well tuned. The great broad‐band nonlinear optical properties indicate hydrazones are good candidates for organic nonlinear optical absorption materials.     

Non‐Resonant z‐Scan Characterization of the Third‐Order Nonlinear Optical Properties of Conjugated Poly(thiophene azines)

The nonlinear optical properties of a functionalized poly(thiophene azine), namely, poly(3,4‐didodecylthiophene azine), PAZ, at the optical telecommunication wavelength of 1550 nm are investigated by means of the closed‐aperture z‐scan technique in both thin films and solutions. Values of χ⁽³⁾=(2.4±0.4)×10^?13 esu, n₂=(4.0±0.7)×10^?15 cm² W^?1, and γ=(4.5±0.7)×10^?34 esu are estimated for the third‐order (Kerr) susceptibility, the intensity‐dependent refractive index, and the molecular second hyperpolarizability of solution samples, respectively. A very small dependence on the polymer chain length is found. Markedly higher values of (4.4±1.1)×10^?11 esu, (6.6±1.0)×10^?13 cm² W^?1, and (5.0±0.8)×10^?33 esu are measured for the corresponding quantities in thick (up to 20 μm) polymer films cast on quartz plates. The enhancement of the NLO responses on going from solution to solid samples is attributed to a partially ordered structure and to the presence of interchain interactions leading to greater π‐electron delocalization in the cast polymer films. The results are compared with those previously obtained by using third‐harmonic generation (THG), taking into account that those data were measured under conditions of three‐photon resonance, whereas our z‐scan measurements are fully off‐resonance.     

Synthesis and Third‐Order Nonlinear Optical Properties of Triphenylene Derivatives Modified by Click Chemistry

A series of asymmetric triphenylene derivatives containing typical D –π–A structures is successfully synthesized by means of [2+2] cycloaddition–cycloreversion click reactions. The photophysical and electrochemical properties, as well as the click reactions, are characterized by means of UV/Vis absorption spectroscopy, cyclic voltammetry, and DFT modulations. In addition, the third‐order nonlinear properties, including the nonlinear absorption and the nonlinear susceptibilities, are investigated by using Z‐scan techniques. A typical reverse saturable absorption–saturable absorption behavior is observed for the third‐order nonlinear absorption, with the third‐order nonlinear susceptibilities of the compounds being 1.05×10^?12, ?1.50×10^?12, and ?0.52×10^?12 esu, respectively.     

Preparation and Optical Limiting Properties of Polyurethane Containing Long Conjugated Chromophores

Two functional polyurethanes (P1 and P2) bearing a large π electron conjugated chromophoric pendant were synthesized and characterized by FT‐IR, ¹H‐NMR and UV‐Vis absorption spectra. Their optical limiting properties were evaluated. The results show that P1 and P2 show novel optical limiting properties, which are assigned to a long π electron conjugated chromophoric pendant. It was found that their optical limiting properties were affected simultaneously by solution concentration and P2 displays a better optical limiting property than P1 at the same solution transmittance, although that P1 has larger χ⁽³⁾ (4.28×10^?11 esu) than P2 (0.87×10^?11 esu), and their optical limiting mechanism is investigated.     

The second and third order non-linear optical properties of liquid crystalline polymers

Abstract

The second and third order non-linear optical susceptibilities of several donoracceptor substituted side chain polymers, some of which exhibit mesophases, will be reported. The susceptibilities were measured by harmonic generation from thin films, typically 0·5 μm thick, at a fundamental wavelength of 1064 nm and 1579 nm. For second harmonic generation, the spin coated films were contact poled on a glass substrate with an interdigited electrode pattern. Typical values obtained were χ⁽²⁾ ₃₁ = 1 × 10^?9 esu and χ⁽²⁾ ₃₃ = 3 × 10^?9 esu, the largest value was χ⁽²⁾ ₃₃ = 6·3 × 10^?9 esu. The difficulty in deriving reliable second order structure-property relations because of the large effect which the contact poling process has on the non-linear optical susceptibility of the films will be highlighted. The highest χ⁽³⁾ value of 5·8 × 10^?12 esu obtained from an amorphous film of a polymer with an asymmetrically substituted azo side group is comparable with the susceptibility of more typical third order non-linear materials such as the main chain polymers polyphenylacetylene and poly-p-phenylenebenzobisthiazole.     

Synthesis,crystal structure and non-linear optical properties of a new cyanide-containing compound

Reaction of K₃[Fe(CN)₆], NiCl₂ and diethylenetriamine (dien) resulted in the formation of a cyanide-containing heterometallic compound [Ni(dien)₂]₂[Fe(CN)₆]·4H₂O 1. The structure consists of two octahedral [Ni(dien)₂]²⁺ cations, one octahedral [Fe(CN)₆]^4? anion and four crystallization water molecules, which are held together by hydrogen-bonding interactions. Its TG curve exhibits two stages of mass loss. Compound 1 in DMF solutions has a very strong third-order non-linear optical (NLO) behavior with an absorption coefficient and refractive index α₂?=?1.10?×?10^?11?m?w^?1, n ₂?=??3.05?×?10^?19?m²?w^?1, respectively, and third-order NLO susceptibility χ⁽³⁾ 4.34?×?10^?13?esu.     

Structures and enhanced third-order nonlinear optical performance of four complexes investigated by thin film <Emphasis Type="Italic">Z-</Emphasis>scan technique

Four transition metal complexes have been synthesized via hydrothermal reactions, namely, [Zn(1,3-BIB)(CH₃COO)₂]₂ 1, [Cu₂(1,4-BIB)₃(CO₃)₂](1,4-BIB)·10H₂O 2, {[Mn(H₂O)₂(1,2-BIB)₂]Cl₂}_n 3, and {[Mn(1,2-BIB)(1,4-NDC)]₂}_n 4, where 1,n-BIB = 1,n-bis(imidazol-l-yl-methyl)benzene, n = 2, 3, 4 and 1,4-NDC = naphthalene-1,4-dicarboxylic acid. Complex 1 presents a discrete ring-like structure. Complex 2 shows a ladder-like chain structure, while complex 3 has a joint-like chain structure. Complex 4 features a layer structure constructed from [Mn₂(N₄O₈)] clusters. The third-order nonlinear optical (NLO) properties of these complexes in thin films have been investigated by employing the Z-scan technique. Complexes 1–3 exhibit strong third-order NLO reverse-saturable absorption, while 4 shows third-order NLO saturable absorption and a strong self-defocusing effect. The third-order NLO susceptibilities χ ⁽³⁾ of the four complexes were calculated as 2.74 × 10^?9, 12.24 × 10^?9, 42.78 × 10^?9 and 189.32 × 10^?9 esu, respectively. The electronic structures of the complexes were investigated by density functional theory, and the origins of their NLO properties are discussed.     

Synthesis,crystal structure,and third-order nonlinear optical properties of a copper(I) one-dimensional coordination polymer

A copper(I) thiocyanate coordination polymer [Cu(Phen)(μ-NCS)]n (I) (Phen = 1,10-phenan-throline) has been synthesized by the low-temperature solid-state reaction. Single-crystal X-ray analyses reveal that compound I possesses a type of one-dimensional (1D) framework structure. Polymer I was characterized by elemental analyses, IR spectra, and UV-visifele spectra. The third-order nonlinear optical properties were also investigated, and they exhibit good nonlinear absorption and self-defocusing performance with modulus of the hyperpolarizability 4.94 × 10⁻³⁰ esu for I in a 6.35 × 10⁻⁴ mol dm⁻³ DMF solution.     

Third-order Nonlinear Optical Properties of Octa-substituted Metal-free Phthalocyanine Thin Films

Third-order nonlinear optical susceptibility, χ⁽³⁾ of symmetrically octa-substituted metal-free phthalocyanine thin films measured by the third-harmonic generation technique are reported. The metal-free phthalocyanine has been found to show a χ⁽³⁾ (−3ω; ω,ω, ω) value as large as 7.73×10⁻¹² esu at 1.80 μm. The figure of merit, χ⁽³⁾/α, was estimated to be 4.17×10¹⁷ esu cm at 1.05 μm and 6.97×10¹⁶ esu cm at 1.65 μm. Both linear and third-order optical properties of liquid-crystalline metal-free phthalocyanines are discussed     

Design and synthesis of polyindole - ZnO nano composite for NLO applications

Present paper mainly focuses on the synthesis, characterization polyindole-ZnO nano composites for third order nonlinear optical applications. Polyindole was synthesized through oxidative polymerization technique and its composites were prepared with different ZnO concentration. Structural morphology of the polymer composite was studied using FESEM, XRD and UV Visible spectroscopic technique. Polymer showed broad absorption with absorption maxima of 395 nm. Newly prepared thin films showed excellent nonlinear absorption with very good optical limiting behaviour when it is exposed to He-Ne laser with maximum optical limiting power of 11 mW along with third-order nonlinear susceptibility χ⁽³⁾ of 2.72 × 10^?3 esu. Hence these polymer composites may be potential candidate for optical limiting applications.     

Synthesis and characterization of photorefractive polymers containing indole groups

Some new photorefractive polymers containing indole groups were synthesized and characterized by IR, ¹H NMR, and UV techniques. The Gibbs free energy changes (ΔG) of corresponding reactions were predicted by density functional theory to be 4.19 and ?9.71 kcal mol^?1 for –H, and 4.12 and ?11.93 kcal mol^?1 for –OCH₃, respectively. The glass transition temperature (T _g) of the polymers were about 96–111 °C. The nonlinear second-order optical susceptibility was predicted to be 2.84 × 10^?30 and 1.04 × 10^?30 esu by theoretical quantum calculations.     

A theoretical investigation of intermolecular interaction of a phthalimide based “on–off” sensor with different halide ions: tuning its efficiency and electro-optical properties

The interaction between chemosensor, N-(2-methyl-1,3-dioxo-indan-5-yl)-benzamide (1) and different halide ions (F ^? , Cl^? and Br^?) has been investigated using density functional theory (DFT). A clear insight of the sensor anion binding process has been presented. Our calculations revealed that the observed colorimetric and fluorescent signals are induced due to the ground state deprotonation of the sensor molecule caused by F^? which has two times higher binding affinity than other halide ions (Cl^? and Br^?). Derivatives of system 1 have been made to find a better sensor with higher binding affinity and longer wavelength of absorption. All the derivatives are better sensors than the parent 1 except 4-methyl-N-(2-methyl-1,3-dioxo-indan-5-yl)-benzamide (2). Among these derivatives, trimethyl-[4-(2-methyl-1,3-dioxo-indan-5-ylcarbamoyl)-phenyl]-ammonium (8) and (5-benzoylamino-1,3-dioxo-indan-2-yl)-trimethyl-ammonium (9) showed a change to higher binding energies of about 58 Kcal/mol and longer absorption wavelengths of 53 nm after deprotonation process than the parent system 1 which is highly demanded in selective chemical sensing. Systems 8, 9 and their deprotonated zwitterionic forms (8z and 9z) have also been studied for their nonlinear optical responses. Systems 8, 9 showed significantly good first hyperpolarizability (β) of 84 × 10^?30 and 40 × 10^?30 esu, respectively. These β values increase in zwitterionic states up to 216 × 10^?30 and 109 × 10^?30 esu, respectively after deprotonation with F^?, representing a new signal of deprotonation.     

Synthesis,characterization, and optical studies of pentoxy-substituted tetrakis(pentafluorobenzyloxy)phthalocyanines

Abstract

The synthesis and characterization of peripherally 2′,3′,5′,6′-tetrafluoro-4′-pentoxy-benzyloxy-substituted metal-free and metallo (Zn(II) and Co(II)) phthalocyanines are described in this study. Aggregation properties of these phthalocyanines were studied in the concentration range of 1 × 10^?5?1 × 10^?6 M in tetrahydrofuran. Thin films of phthalocyanines were prepared by spin-coating technique. The spectrophotometric measurements of transmittance spectra were carried out in the wavelength range of 200–1000 nm. Optical band gaps of phthalocyanine thin films were also calculated. Surface morphologies and thickness of the films were examined by Scanning Electron Microscopy. Results show that film thickness can be changed significantly depending on the type of metal in the phthalocyanine.     

Conductive and optical properties of PPV modified by N+ ion implantation

In this article, a soluble poly[2‐methoxy‐5‐(3′‐methyl)butoxy]‐p‐phenylene vinylene (MMB‐PPV) was synthesized by dehydrochlorination reaction and the MMB‐PPV film was implanted by nitrogen ions (N⁺) with the ion dose and energy in the range of 3.8 × 10¹⁵ to 9.6 × 10¹⁶ ions/cm² and 15–35 keV, respectively. The surface conductivity, optical absorption, optical band gap (E_g) of modified MMB‐PPV film were studied, and the third‐order nonlinear optical susceptibility (χ⁽³⁾) as well as its environmental stability of modified MMB‐PPV film were also measured by degenerate four‐wave mixing system. The results showed that the surface conductivity of MMB‐PPV film was up to 3.2 × 10^?2 S when ion implantation was performed with the energy of 35 keV at an ion dose of 9.6 × 10¹⁶ ions/cm², which was seven order of magnitude higher than that of the pristine film. UV‐Vis absorption spectra demonstrated that the optical absorption of MMB‐PPV film was enhanced gradually in the visible region followed by a red shift of optical absorption threshold and the E_g value was reduced from 2.12 eV to 1.59 eV with the increase of ion dose and energy. The maximum χ⁽³⁾ value of 2.45 × 10^?8 esu for modified MMB‐PPV film was obtained with the ion energy of 20 keV at an ion dose of 3.8 × 10¹⁶ ions/cm², which was almost 33 times larger than that for pristine film. In comparison to the reduction of 17% in the χ⁽³⁾ value of pristine MMB‐PPV film, the maximum χ⁽³⁾ value of 2.45 × 10^?8 esu for modified MMB‐PPV film decreased by over 5.3% when they had been exposed under the same ambient conditions for 90 days. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2072–2077, 2010     

One-pot synthesis,characterization, DNA binding and enzymatic studies of 4-methyl trans-cinnamate zinc(II)-mixed ligand complexes

Four new zinc(II) complexes formulated as [Zn(L)₂] (1), [Zn(L)₂(phen)] (2), [Zn(L)₂(bipy)H₂O] (3), and [Zn(en)₂(H₂O)₂](L)₂(H₂O)₂ (4), where HL = 4-methyl trans-cinnamic acid, bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline, and en = ethylenediamine, have been synthesized and characterized by FT-IR and NMR spectroscopy. Single-crystal XRD revealed distorted square-pyramidal structure for 3 and octahedral for 4. The complexes were screened for DNA interaction via viscommetry and UV–visible spectroscopy. The apparent binding constants were calculated to be 1.18 × 10⁴, 1.26 × 10⁵, 4.64 × 10⁴_, and 1.89 × 10⁴ for 1–4, respectively. The binding propensity to salmon sperm DNA was in the order: K₂ > K₃ > K₄ > K₁. Furthermore, these complexes demonstrated efficient inhibition of alkaline phosphatase, which was attributed to the binding of zinc(II) to the enzyme’s active site.     

Two-Photon Absorption and Excited-State Refractions in Anthraquinone Dyes

We examine the nonlinear optical properties of solutions of 9,10-anthraquinone, 1,4-dihydroxy-anthraquinone, 5,8-dichloro-1,4-dihydroxy-anthraquinone and 1,4-bisethylamino-anthraquinone by means of the intensity-dependent transmission and the Z-scan method with 532 nm 8 ns pulses. The results demonstrated that the 9,10-anthraquinone displayed a two-photon absorption (TPA) character. The molecular TPA cross section of this compound is estimated as σ₂ = 7.22 × 10^?19 cm⁴/GW or σ₂ = 26.96 × 10^?48 cm⁴/photon/s, respectively, and an essential state of ‘m¹Ag’, which should be located near the 2ω virtual transition state, is predicted. On the other hand, the effective excited-state nonlinear refractive coefficients n₂^eff of these anthraquinones are found to be ～10^?10 esu, which are comparable with those highly conjugated planar molecules of tetrabenzporphyrins and phthalocyanines.     

四叔丁基萘酞菁铅化合物的非线性和光限幅特性

合成了四叔丁基萘酞菁铅[(t-Bu)₄NcPb]化合物. 利用元素分析、红外光谱、核磁共振氢谱等方法, 验证了化合物的分子结构. 应用调Q倍频ns/ps Nd:YAG脉冲激光系统, 在波长为532 nm下, 研究了化合物的非线性和光限幅特性. 测得化合物的非线性折射率n₂和三阶非线性极化率χ⁽³⁾分别为2.42×10^－11和7.91×10^－12 esu, 通过计算得到分子极化率γ'为3.4×10^－29 esu. 在透过率69%时限幅阈值为1522 mJ/cm², 箝位值为553 mJ/cm², 有效激发态与基态吸收截面比为3.16.