Synthesis and strong optical limiting response of graphite oxide covalently functionalized with gallium phthalocyanine

A soluble graphite oxide (GO) axially substituted gallium phthalocyanine (PcGa) hybrid material (GO-PcGa) was for the first time synthesized by the reaction of tBu(4)PcGaCl with GO in anhydrous DMSO at 110?°C in the presence of K(2)CO(3). The formation of a Ga-O bond between PcGa and GO has been confirmed by x-ray photoelectron spectroscopy. In contrast to GO, the D and G bands of GO-PcGa in the Raman spectrum are shifted to the lower wavenumbers by Δν = 11 and 18 cm(-1), respectively. At the same level of concentration of 0.1 g l(-1), GO-PcGa exhibit much larger nonlinear optical extinction coefficients and strong optical limiting performance than GO, tBu(4)PcGaCl and C(60) at both 532 and 1064 nm, implying a remarkable accumulation effect as a result of the covalent link between GO and PcGa. GO-PcGa possesses three main mechanisms for the nonlinear optical response-nonlinear light scattering, two-photon absorption and reverse saturable absorption for the 532 nm pulses and nonlinear light scattering for the 1064 nm pulses. tBu(4)PcGaCl does not make any significant contribution to the optical limiting at 1064 nm, while GO-PcGa has a much greater optical limiting response than GO at this wavelength, this suggesting that the PcGa moiety could certainly play an unknown but important role in the GO-PcGa material system.     

Encapsulation of aromatic oxygen palladium phthalocyanine in silica xerogel and its optical limiting property

Metallophthalocyanines (MPc) exhibit, among many useful properties, the ability to protect sensors against short, intense pulse deleterious to efficient sensor operation. For the successful application of this optical limiting property, an important issue is the incorporation of MPc molecules in a matrix to fabricate a solid state system. We report here the study of different concentrations of aromatic oxygen palladium phthalocyanine (ArOPdPc) encapsulated in silica xerogel obtained by the sol–gel technique. The resulted composites were transparent and homogeneous with the required optical limiting properties. The trapping effect was confirmed by the characteristic absorption bands of ArOPcPd in the UV–Vis spectra. The optical limiting properties of the composites were measured at 532 nm with 8 ns pulses. The results showed that the composites had obviously optical limiting effect, owing to the existing of large amount of monomers and the introduction of palladium atom in the cavity of phthalocyanine ring.     

Structural and optical properties of thermally evaporated zinc phthalocyanine thin films

Thermally evaporated zinc phthalocyanine (ZnPc) films in the as deposited condition were identified to be as-amorphous. It undergoes structural transformation upon annealing up to 613 K. The optical properties and spectral behavior of as deposited and annealed thin films of ZnPc were studied using spectrophotometric measurements of the transmissivity and reflectivity at normal incidence of light in the wavelength range 200–2500 nm. The refractive index, n, and absorption index, k, were calculated and it was found that they are independent of film thickness in the thickness range 205–530 nm. Annealing at 613 K increases absorbance of films by 5–6 times in comparison with absorbance of as deposited ones and shifts peak positions of all bands towards low energy side of spectra except the peak position of N-band is shifted towards high energy side of spectra. The absorption spectra in the UV–VIS. region has been analyzed in terms of both molecular orbital and band theories. Indirect allowed transitions near the onset and fundamental absorption edges were observed. The energy at the onset was obtained and equals to 1.45 and 1.51 eV for as deposited and annealed films, respectively. The fundamental energy gap was obtained and equals to 2.94 and 2.88 eV for as deposited and annealed films, respectively. The absorption spectra shows four absorption bands. The oscillator strength, f, the electric dipole strength, q², the molar extinction coefficient, ζ_molar, were calculated for as deposited and annealed ZnPc thin films.     

Microstructure of nanoscale zinc oxide crystallites

Nanosized ZnO particles were prepared using a simple precipitation method. First, hydrozincite was obtained by adding Na₂CO₃ aqueous solutions with different concentrations to a zinc acetate precursor, previously dissolved in ethanol. We observed that the starting concentration of the precursors and the water content used for the hydrolysis influenced the size of the hydrozincite particles. The formation of the ZnO nanoparticles began after heating the hydrozyncite to 200 °C, and even when heating to 600 °C nanosized ZnO particles of 20-50 nm were obtained without agglomeration. The morphology and crystallinity of the obtained solids were characterized using XRD, SEM and TEM.     

Recent research progress on optical limiting property of materials based on phthalocyanine, its derivatives, and carbon nanotubes

Carbon nanotubes and organic compounds with extensive delocalized π-electron system such as phthalocyanine and its derivatives are attracted much attention as potential optical limiting materials. In this article, the optical limiting properties of carbon nanotubes, phthalocyanine as well as its derivatives and modifying approaches to improve their optical limiting performance are reviewed. In addition, the optical limiting properties exhibited by the nanohybrids obtained from the combination between carbon nanotubes and phthalocyanine or its derivatives are also introduced.     

Enhanced open-circuit voltage in organic photovoltaic cells with partially chlorinated zinc phthalocyanine

The open-circuit voltage (V _OC) in organic photovoltaic cells has been shown to depend on a number of parameters including the energy levels of the active materials, active layer structure, illumination intensity, and operating temperature. Here we report, a significant increase in V _OC from 0.43 to 0.63 V in zinc phthalocyanine (ZnPc)/C₆₀ planar heterojunction photovoltaic cells operated at room temperature under 1 sun AM1.5G solar illumination, when a home-synthesized and purified ZnPc source materials was used instead of a commercially obtained (and home purified) ZnPc source. While the two ZnPc source materials have nearly identical UV–Vis and IR absorption properties, the home-synthesized ZnPc contains chlorinated derivatives and has half of the electrical defect density (on the order of 10¹⁶ cm^?3) as compared to the commercial ZnPc. The improved V _OC in devices with the home-synthesized ZnPc is contributed from both a lower dark current and a higher magnitude of photocurrent. Additional experiments revealed that the different device characteristics are mostly associated with processes occurring at the ZnPc/C₆₀ interface, which we attribute to nongeminate recombination of charges built-up on either side of the interface.     

Space charge analysis in doped zinc phthalocyanine thin films

We present an improved method for the determination of the space charge density in organic semiconductors used as active layers in Schottky barriers. These measurements provide a powerful tool for the interpretation of basic properties such as the rectifying effect, doping process and carrier trapping mechanisms of films together with a way to assess the potential for sensor applications. Metal/molecular semiconductor Schottky junctions were prepared on zinc phthalocyanine layers doped by a controlled exposure to the ambient air. The organic material is deposited on aluminium or heavily doped silicon substrates, in order to make a Schottky barrier (film thickness around 1 μm). An ohmic contact is obtained by a gold deposition on the strongly doped side of the molecular material. We have investigated the current-voltage and capacitance-voltage characteristics. The results are interpreted in terms of a space charge region at the interface with the substrate, followed by an extended semi-insulating layer.The contribution of these two regions to the total impedance is analyzed in well improved conditions of measurements.     

Electrical and optical properties of phthalocyanine films

Thin films of various phthalocyanines (Pcs) were sublimed onto quartz glass in ultrahigh vacuum. The electrical and optical properties were studied without breaking the ultrahigh vacuum. The dyes were purified by repeated sublimation in vacuum.The conductivity varied with pretreatment (modification) and temperature. Exposure to oxygen, iodine and bromine increased the p-type conductivity by orders of magnitude and lithium doping caused n-type conductivity. Heavy exposure to halogens caused not only broadening of the optical absorption band but also bleaching. Annealing in vacuum removed the electrical and optical effects of doping nearly completely.Field effect studies were used to identify p- and n-type conductivity, to determine the drift mobility and to estimate the trap densities. The field effect and the photoconductivity of p- and n-type films increased by several orders of magnitude with the dark conductivity, i.e. with doping. This correlation is attributed either to traps with a continuous distribution in energy or to trapping by at least two discrete defect levels crossing the Fermi level within the surface-induced accumulation layer. Possible consequences for the sensitivity of semiconductor gas sensors are discussed.     

Parametric uncertainty in nanoscale optical dimensional measurements

Image modeling establishes the relation between an object and its image when an optical microscope is used to measure the dimensions of an object of size comparable to the illumination wavelength. It accounts for the influence of all of the parameters that can affect the image and relates the apparent feature width (FW) in the image to the true FW of the object. The values of these parameters, however, have uncertainties, and these uncertainties propagate through the model and lead to parametric uncertainty in the FW measurement, a key component of the combined measurement uncertainty. The combined uncertainty is required in order to decide if the result is adequate for its intended purpose and to ascertain if it is consistent with other results. The parametric uncertainty for optical photomask measurements derived using an edge intensity threshold approach has been described previously; this paper describes an image library approach to this issue and shows results for optical photomask metrology over a FW range of 10 nm to 8 μm using light of wavelength 365 nm. The principles will be described; a one-dimensional image library will be used; the method of comparing images, along with a simple interpolation method, will be explained; and results will be presented. This method is easily extended to any kind of imaging microscope and to more dimensions in parameter space. It is more general than the edge threshold method and leads to markedly different uncertainties for features smaller than the wavelength.     

聚合物光限幅材料的研究

随着现代激光技术和武器的快速发展,急需激光防护材料(光限幅材料)和设备来防护人眼和光学传感设备免受激光的破坏.由于高分子光限幅材料具有大的非线性光学性能、快速的光学响应、高的损伤阈值和好的加工性能引起人们的广泛兴趣. 在这篇论文中,从分子结构以及分子结构对光限幅性能和光限幅机制的影响,对高分子光限幅材料进行了详细的综述,并提出高分子光限幅材料未来的发展方向.     

Structural aspects of Langmuir-Blodgett and cast films of zinc phthalocyanine and zinc hexadecafluorophthalocyanine

The processing of macrocyclic phthalocyanines (Pc) in the form of thin, nanostructured films has been usually carried out via evaporation techniques, owing to the low solubility exhibited by these compounds. The fabrication of Pc ultrathin films via the Langmuir-Blodgett technique may be advantageous from a technological point of view, since parameters such as film architecture and organization can be achieved without post-thermal treatments. In this study, a parent zinc phthalocyanine (ZnPc) and its fluorinated derivative (F₁₆ZnPc) were synthesized and manipulated in the form of LB films. The morphological and structural features of ZnPc and F₁₆ZnPc Langmuir-Blodgett films containing up to 31 layers were investigated using Fourier transform infrared spectroscopy (FTIR), micro-Raman spectroscopy and X-ray diffraction analyses and were compared to ZnPc and F₁₆ZnPc cast films. The interplanar distance obtained by X-ray specular reflection decreases from 12.64 Å for ZnPc to 12.16 Å for F₁₆ZnPc. FTIR spectra indicated absence of order in the LB films from ZnPc and F₁₆ZnPc, at least in the direction perpendicular to the substrate surface. Therefore, the order observed in the X-ray diffractograms means that the molecules might be organized in crystallites that are randomly oriented in the film.     

锌酞菁接枝温敏水凝胶的制备及光活性

将具有较高光催化活性的反应型锌酞菁负载到温敏聚合物——聚(N-异丙基丙烯酰胺)水凝胶载体上,制得一种新型的温敏高分子催化剂。研究了酞菁接枝水凝胶的温敏性能,发现其对温度有明显的依赖性和响应性。通过对α-萘酚进行光催化氧化实验,发现其在可见光照射下具有较高的光催化活性,气质分析得到其氧化产物主要是邻苯二甲酸。另外,循环实验表明该催化剂具有较好的稳定性,可重复使用。     

Optical recording behavior of tetra-neopentoxy phthalocyanine zinc Langmuir-Blodgett film

Langmuir-Blodgett films of tetra-neopentoxy phthalocyanine zinc (TNPPcZn) were prepared. Static optical recording behavior was tested in the Langmuir-Blodgett films of TNPPcZn. The reflectivity contrast was more than 100% in a writing and erasing cycle experiment. This is the first time to our knowledge that writing and erasing experimental data have been obtained in TNPPcZn film.     

Controlling optical gain in semiconducting polymers with nanoscale chain positioning and alignment

We control the chain conformation of a semiconducting polymer by encapsulating it within the aligned nanopores of a silica host. The confinement leads to polarized, low-threshold amplified spontaneous emission from the polymer chains. The polymer enters the porous silica film from only one face and the filling of the pores is therefore graded. As a result, the profile of the index of refraction in the film is also graded, in the direction normal to the pores, so that the composite film forms a low-loss, graded-index waveguide. The aligned polymer chains plus naturally formed waveguide are ideally configured for optical gain, with a threshold for amplified spontaneous emission that is twenty times lower than in comparable unoriented polymer films. Moreover, the optimal conditions for ASE are met in only one spatial orientation and with one polarization. The results show that nanometre-scale control of semiconducting polymer chain orientation and position leads to novel and desirable optical properties.     

Electrical and structural properties of ortho-chloranil doped zinc phthalocyanine films

Electrical conductivity of evaporated zinc phthalocyanine (ZnPc) films, doped with orthochloranil (o-CA) molecules, is investigated. Benzoico-CA solution is introduced in the film and benzene is removed by vapourization afterwards. The film conductivity at first increased and then decreased with incremental doping. The maximum conductivity of the sample appeared at doping level × (=o-CA/ZnPc) 0.2 and is about 10³ times as large as that of the as-evaporated one. About a ten-fold further increase in the conductivity is obtained by the heat-treatment of 150 °C for 12 h. The conductivity change by doping is explained by taking into account thato-CA molecules behave not only as acceptors in the film but destructively for the film structure. The phase change of ZnPc by benzoic solution is also discussed.     

Viscosity dependence of optical limiting in carbon black suspensions

We measure the optical limiting behavior of carbon black suspensions in various viscosity solvents by using a 10-Hz repetition rate, 532-nm, 5-ns pulsed laser. We found that, for common solvents used in the past such as water and ethanol, the limiting behavior ceases after a few laser firings and a turnover in the limiting curve appears. This can be explained by depletion of the carbon black within the focal volume. This turnover shifts to lower energies as the viscosity of the solvent becomes greater. However, for low viscosity liquids, such as carbon disulfide or pentane, the limiting is unaffected by the repetition rate, at least for frequencies up to 10 Hz, because of diffusion of the carbon black particles. This diffusion allows fresh material to replace the irradiated volume within the time between pulses.     

Physical and optical properties of phthalocyanine doped inorganic glasses

Physical and optical properties of various free base and metallic phthalocyanine (Pc) doped glass matrix are reported for the first time. Absorption spectral measurements of H₂Pc, MnPc, NiPc, CoPc, CuPc, MoOPc, ZnPc and FePc doped borate glass matrix have been made in the 200–1100 nm region and the spectra obtained are analyzed in the 2.1–6.2 eV region to obtain the optical band gap (E_g) and the width of the band tail (E_t). Other important optical and physical parameters viz. refractive index (n), molar extinction coefficient (), density (), glass transition temperature (T_g), molecular concentration (N), polaron radius (r_p), intermolecular separation (R), molar refractivity (R_m) are also reported.     

Fluorescence and nonlinear optical properties of non-aggregating hexadeca-substituted phthalocyanine

Highly non-aggregating hexadeca-substituted phthalocyanine (Pc) complexes were prepared and their fluorescence and nonlinear optical properties were studied. Three visible fluorescence bands were observed when the Pc complexes were excited at 355 nm and found to be concentration dependent. They are attributed to the optical transitions S₂ → S₀ at 415 nm, T₂ → T₁ at 630 nm, and S₂ → S₁ at 755 nm. Nonlinear absorptive and refractive effects were measured with the help of Z-scan technique. Saturation absorption was observed at 632.8 nm where the nonlinear absorption coefficient is found to be very large (β = −2.8 × 10⁻² cm/W) and the refractive nonlinear coefficient γ = −9.5 × 10⁻¹¹ cm²/W. In the transparency domain at 532 nm, reverse absorption saturation is observed and β and γ are found to be 17.5 and 15.5 times smaller, respectively. Optical limiting performances are measured in the absorption and transparency domains. Purely refractive-based optical limiting at 632.8 nm is found to have a threshold of 0.16 kW/cm², lower than the reverse absorption saturation and refractive-based optical limiting of 0.90 kW/cm² at 532 nm.