Indium(III) and Gallium(III) phthalocyanines-based nanohybrid materials for optical limiting

Linear and nonlinear optical properties of a phthalocyanine (Pc)-based nanohybrid material PCIGS [Cu₂(tBu₄PcGa)(tBu₄PcIn)S₂TPP₂] are described. The overall aggregation of phthalocyanines in poly(methylmethacrylate) (PMMA) films was evident, which is indicated by the broadening of linear spectra in the Q-band region and the shift of wavelength. Upon excitation with nanosecond laser pulse at 355 nm, the transient absorption band appeared at about 500 nm is attributed to the triplet–triplet absorption of the Pcs. For PCIGS and its starting materials tBu₄PcGaCl and tBu₄PcInCl, all Z-scans exhibit a decrease in transmittance about the focus typical of an induced positive nonlinear absorption of incident light. The absorption mechanism is due to population of excited states through a multi-step nonlinear absorption. When these Pc compounds were embedded into a commercially available polymer PMMA, all the Pc/PMMA composites display much larger nonlinear absorption coefficient and lower saturable fluence for optical limiting when compared to the same Pc molecules in solution. However, in contrast to tBu₄PcGaCl and tBu₄PcInCl, PCIGS displayed decreased optical limiting response, possibly due to competing electron accepting processes in the In and Ga metals, and the highly ordered structure of the PCIGS complex itself.     

Electrochemistry of Poly(3,4‐alkylenedioxythiophene) Derivatives

An overview of the electrochemistry of poly(3,4‐alkylenedioxythiophene)s (PXDOTs) is presented. As a class of conducting and electroactive polymers that can exhibit high and quite stable conductivities, a high degree of optical transparency as a conductor, and the ability to be rapidly switched between conducting doped and insulating neutral states, PXDOTs have attracted attention across academia and industry. Numerous fundamental aspects are addressed here in detail, ranging from the electrochemical synthesis of PXDOTs, a variety of in‐situ characterization techniques, the broad array of properties accessible, and morphological aspects. Finally, two electrochemically‐driven applications, specifically electrochromism and chemical sensors of PXDOTs are discussed.     

Enhanced photoluminescence of Gd0.94(P1−xVx)O4:Eu0.06 red-emitting (0 ≤ x ≤ 1.0) phosphors

High-quality Gd_0.94(P_1−xV_x)O₄:Eu_0.06 (0 ≤ x ≤ 1.0) powders having small size, spherical morphology, smooth surface, and nonaggregation are synthesized by the ultrasonic spray pyrolysis. The complex host composition, Gd_0.94(P_1−xV_x)O₄:Eu_0.06 (x ≥ 0.5), shows a single phase with the tetragonal xenotime structure. The introduction of V⁵⁺ ions in the P⁵⁺ lattice yields the deviation from the centrosymmetry of Eu³⁺ ions. By increasing the V⁵⁺ content, the emission intensity corresponding to the ⁵D₀ → ⁷F₁ transition decreases. On the other hand, the emission intensity corresponding to the ⁵D₀ → ⁷F₂ transition increases up to x = 0.5, and then decreases upon further increasing the V⁵⁺ content. The emission intensity, peaking at 620 nm, of complex composition Gd_0.94(P_0.5V_0.5)O₄:Eu_0.06 is approximately five and two times stronger than that of the Gd_0.94PO₄:Eu_0.06 and Gd_0.94VO₄:Eu_0.06, respectively. It is believed that the introduction of the complex composition Gd_0.94(P_1−xV_x)O₄:Eu_0.06 is highly effective for improving the emission properties.     

Preparation of gold nanosheets using poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) block copolymers via photoreduction

Gold nanosheets having single crystalline structure were successfully synthesized using the bulk phase mixture of HAuCl₄ and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) block copolymers through the irradiation of a glow lamp for 5 days. When the molar ratio of propylene oxide to ethylene oxide block units in the block copolymer is about 1.75, mostly gold nanosheets were obtained. Gold nanosheets with an average width of 8 and 5 μm were obtained from the when the molar ratio of gold salt to the ethylene oxide units in the block copolymer were 1/80 and 1/160, respectively.     

Characterization and investigation of the mesogenic, thermo-morphologic and thermotropic properties of new chiral (S)-5-octyloxy-2-[{4-(2-methylbuthoxy)-phenylimino(methyl]phenol liquid crystalline compound

Synthesis, characterization and investigation of the mesogenic, thermo-morphologic and thermotropic properties of a new chiral liquid crystalline compound are presented in this work. This new compound has prolate molecules and exhibits the chiral smectic C* mesophase in a sufficiently large temperature interval. Two types of solid crystalline phases have been found in this compound. Typical textures and temperatures of the direct and reverse phase transitions, taking place in the compound, are given. Typical peculiarities for the first-order transition between the smectic C* mesophase and isotropic liquid have been observed.     

Materials for Bio‐inspired Optics

Bio‐inspired optical systems have the potential to transform the process of image collection and analysis in the future. Through simplicity and dynamics these collection systems may provide multiple functions with an excellent level of reliability. From the graded index of the fish‐eye to the hyper‐acuity of the compound eye, nature has provided function with amazing simplicity. This article reviews a select number of biological vision systems and the unique material behaviors that rise to these characteristics. We introduce the materials chemistry and morphological complexity that enables the biological system behavior.     

Compositional dependence of refractive index and oscillator parameters in TlGaS2xSe2(1−x) layered mixed crystals (0 ≤ x ≤ 1)

Optical characterization of TlGaS_2xSe_2(1−x) mixed crystals have been carried out at room temperature using the transmission and reflection measurements in the wavelength range of 400–1100 nm. The spectral dependence of the refractive index for all compositions of studied crystals were obtained. The dispersion of the refractive index is discussed in terms of the Wemple–DiDomenico single-effective-oscillator model. The compositional dependencies of refractive index dispersion parameters: oscillator energy, dispersion energy and zero-frequency refractive index were revealed.