Transparent Glass Films Research Articles

Cyclic Perfluoropolyether: Distinct Film Formability and Thermostabilization Upon Recyclable Cyclic-Linear Topological Transformation.

Perfluoropolyether (PFPE) is an industrially important fluoropolymer and has great industrial importance due to its flexible, noncombustible, and chemically robust properties. However, exploration and application of chemically modified homogeneous PFPEs are hampered by their immiscibility against nonfluorine-containing molecules. Here, the synthesis is reported of cyclic PFPE with hexaarylbiimidazoles (HABIs) in chains from linear PFPE having 2,4,5-triphenylimidazole (lophine) end groups. While phase separation between the end groups and main chains took place for linear PFPE, HABIs and main chains in cyclic PFPE are miscible to form transparent glass films. The design of cyclic PFPE also enables cyclic to linear topological transformation based on conversion of HABIs into lophines upon mild heating in the glass film state. Sequential linear-to-cyclic and cyclic-to-linear topological transformations enable fabrication of thermostabilized transparent films derived from PFPE.

𝛍m-resolution thickness distribution measurement of transparent glass films by using a multi-wavelength phase-shift extraction method in the large lateral shearing interferometer.

In this paper, a precise phase-shift extraction method was introduced for the first time to measure the thickness distribution of transparent glass films. A spatial light modulator modulated the phases of the incident laser in a large lateral shearing interferometer. The phase shifting caused by the thickness of the films can be extracted ranging from 0 to 2π, in a recursive way suitable for real-time implementation. Incident lasers with different wavelengths were utilized to measure the spatial distribution of the thickness of the films, and they can be larger than one wavelength of the incident light. Both artificial and experimental results have verified that the resolution of the thickness measurement reaches up to 1 𝛍m.

Improvement in Durability of Red Phosphor Encapsulated by Sol-Gel Glass for Use in White Light-Emitting Diodes

Transparent glass films with homogeneously doped light emissive molecules can be prepared by using the sol-gel process. As part of our work on improving the durability of water-soluble polysilanes against UV light irradiation, we fabricated Eu(TTAhPhen-doped sol-gel glasses and studied their optical characteristics. Using a three dimensionally dense glass network protects the Eu complex from free oxygen and water in an ambi­ ent and also improves the durability without any loss of light output. By adding the Eu(TTAhPhen beyond the limit of solubility in a starting solution, we demonstrated that the glass encapsulation prevents oxidation of the Eu-complex and also preserves its excitation intensity at a wavelength of 400 nm.

Improved Durability of Eu Chelate Encapsulated by Silica Glass Film Prepared by Sol-Gel Method

We demonstrated an improved durability of Eu(HFA)3(TPPO)2 [tris(hexafluoroacetylacetonato)- europium(III) 1,2-phenylenebis(diphenylphosphine oxide)] encapsulated by a sol-gel derived silica glass film. The film was constructed using phenyltrimethoxysilane and diethoxy- dimethylsilane as a starting solution. Unlike cases in which conventional tetramethoxysilane is used, no decrease in internal quantum efficiency was observed at room temperature. We further improved the thermal and long-term stability of Eu(HFA)3(TPPO)2 inside the transparent glass film at elevated annealing temperatures when compared to the Eu(HFA)3(TPPO)2 powder itself: The photoluminescence quantum efficiency of the transparent film was 60% at 160℃ and 32% at 20℃. Properly prepared glass networks protect the Eu chelate from free oxygen and water in the transparent glass film, which is promising for future practical applications.

Improvement in Durability of Red Phosphor Encapsulated by Sol-Gel Glass for Use in White Light-Emitting Diode

Transparent glass films with homogeneously doped light emissive molecules can be prepared by using the sol-gel process. As part of our work on improving the durability of water-soluble polysilanes against UV light irradiation, we fabricated Eu(TTA)3Phen-doped sol-gel glasses and studied their optical characteristics. Using a three dimensional dense glass network protects the Eu complex from free oxygen and water in an ambient and also improves the durability without any loss of light output. By adding the Eu(TTA)3Phen beyond the limit of solubility in a starting solution, we demonstrated that the glass encapsulation prevents oxidation of the Eu-complex and also preserves its excitation intensity at a wavelength of 400 nm.

Fabrication of Optically Active Er3+-Doped Bi2O3–SiO2 Glass Thin Films by Pulsed Laser Deposition

We examined the fabrication conditions of optically active Er3+-doped Bi2O3–SiO2 glass thin films prepared by pulsed laser deposition using a glass target with a nominal composition (mol %) of 41Bi2O3·57SiO2·2Er2O3. The transparent glass films were obtained at 200 °C under 5 ×10-2 Torr O2. The glass films were found to possess a composition and a refractive index close to those of the bulk glass used as the target. The films exhibited a broad emission of Er3+ ions at around 1.5–1.6 µm as well as Er3+ upconversion-pumped fluorescence in the 500–700 nm range.

Quantitative Analysis of the Photodegradation of Emitting CdTe Nanocrystals Dispersed in Glass Films

CdTe nanocrystals (NCs, green- and red-emitting) prepared by an aqueous method were embedded into transparent glass films (15-20 microm thick) using a sol-gel method. Photodegradation of the NCs in the films due to UV irradiation (365 nm) was investigated quantitatively by measuring the PL efficiency as a function of the irradiation time for various irradiation intensities at several temperatures. Since CdTe NCs prepared by an aqueous method incorporate sulfur atoms from the surfactant (thioglycolic acid) during prolonged reflux in an alkaline region, the surface of red-emitting NCs (3.9 nm phi) is much more sulfur rich than that of green-emitting ones (2.6 nm phi), as previously reported. Due to this composition difference, the degradation behaviors of the two types of NCs differ significantly. The photodegradation of green-emitting glass films depended linearly on the irradiation intensity, whereas that of red-emitting ones showed a quadratic dependence. The activation energies of the photodegradation for both types of films were similar, 304 +/- 9 and 288 +/- 7 meV/particle, respectively. The NCs in the film were more than 2 orders of magnitude more robust than those in colloidal solutions. Comparison of the degradation of the glass films in air and in an Ar atmosphere revealed that the main mechanism of the photodegradation of the green-emitting NCs was oxidization from the first electronically excited state. The mechanism of the red-emitting NCs was not oxidization but a surface change probably related to a surfactant reaction.

Direct Deposition in Film Form of Arsenic-Sulfur Glasses by Evaporation under Normal Pressure

Arsenic-sulfur glasses can be directly prepared in the film form by thermal evaporation under normal pressure employing an evaporation outfit devised so as to prevent oxidation by atmospheric gas. The prevention of oxidation is made by contacting a plane target of a moderate thickness with the top edge of batch container. The moderate thickness of target is in the neighborhood of 0.05mm when the target material is aluminum.The preparation of transparent glass films requires control of the target temperature. In general, during an evaporation the batch has been heated up to 120°-150°C higher than the target temperature. In the case of As2S3 batch, target temperatures below about 345°C have been resulted in opaque and/or crystalline films whereas at temperatures of 345°-365°C transparent glass films of good quality have been obtained. Target temperatures above about 365°C, however, cause the formation of bubbles in the film. Transparent glass films can be successively obtained by replacing the target during the continuous evaporation. The optimum temperature of target is shifted toward the lowered temperature and at the same time the optimum temperature range is widened with the increase in the sulfur content of batches. In the case of the batch of As2S3+11S in mole ratio, the optimum range of target temperature has been 250°-290°C. The direct preparation of transparent glass films from the batch mixture of arsenic and sulfur can be made by the almost the same temperature control of target as in the case of the batch of As2S3-S system. The rate of deposition of the glass films has been about 0.01mm/min. when the difference in temperature was 120°-150°C between target and batch. When the material of target is aluminum, the dissolution of the target in dilute hydrochloric acid is one of the convenient ways of separating the glass film from the target. In this way, transparent glass films of 0.05-0.3mm thickness have been successfully obtained without special care.The arsenic content of transparent glass films obtained is increased with that of batches, and is increased with raising the target temperature within the optimum range. The arsenic content of the glass films is increased to some extent by the continuous evaporation and successive depositions of the film on new targets. The composition of the films obtained from As2S3 batch has been in the range of about 59 weight% arsenic (As2S3.2) to about 63 weight% arsenic (As2S2.7), and the compostion of the films from As2S3+11S batch in the range of about 23 weight% arsenic (As2S16) to about 37 weight% arsenic (As2S8). In this paper, the arsenic-sulfur mole ratios are expressed in the form of formulas for each glass film.The X-ray diffraction measurements on the transparent films of the compositions near to As2S3 and As2S8 and on the ircrushed powders show that these films are glassy. A few additional properties observed from glass films of the composition ranging from As2S2.7 to As2S8.2 are as follows: Infrared transparent up to about 12μ (transmission=about 70%); no appearance of devitrification after the heat treatment in moist air at about 95°C for 9 hours and/or after the exposure to moist air at room temperature for 1 year; inert to both hot water and 10 weight% hydrochloric acid at about 95°C (weight loss after 9 hours=10-4-10-5g/100g of reagent); high electric resistivity (volume resistivity at room temperature=1015-1016 ohm-cm).