scholarly journals Anisotropic bending and twisting behavior of a twin crystal composed of a diarylethene

CrystEngComm ◽  
2021 ◽  
Author(s):  
Takuya Higashiguchi ◽  
Daichi Kitagawa ◽  
Seiya Kobatake
Keyword(s):  
Uv Light ◽  
Incident Light ◽  
Twin Crystal

Here, we found that crystals consisting of 1,2-bis(2-methyl-5-(4-undecyloxyphenyl)-3-thienyl)perfluorocyclopentene (1a) exhibit unusual photomechanical bending. Upon irradiation with ultraviolet (UV) light, the crystal bent toward the incident light, but the velocity of...

scholarly journals Photooxidation of Cyclohexane by Visible and Near-UV Light Catalyzed by Tetraethylammonium Tetrachloroferrate

Catalysts ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 403
Author(s):  
Kira Fahy ◽  
Adam Liu ◽  
Kelsie Barnard ◽  
Valerie Bright ◽  
Robert Enright ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Reaction Rate ◽  
Uv Light ◽  
Incident Light ◽  
Reaction Conditions ◽  
Primary Products ◽  
Photonic Efficiency ◽  
Quenching By Oxygen

Tetraethylammonium tetrachloroferrate catalyzes the photooxidation of cyclohexane heterogeneously, exhibiting significant photocatalysis even in the visible portion of the spectrum. The photoproducts, cyclohexanol and cyclohexanone, initially develop at constant rates, implying that the ketone and the alcohol are both primary products. The yield is improved by the inclusion of 1% acetic acid in the cyclohexane. With small amounts of catalyst, the reaction rate increases with the amount of catalyst employed, but then passes through a maximum and decreases, due to increased reflection of the incident light. The reaction rate also passes through a maximum as the percentage of dioxygen above the sample is increased. This behavior is due to quenching by oxygen, which at the same time is a reactant. Under one set of reaction conditions, the photonic efficiency at 365 nm was 0.018 mol/Einstein. Compared to TiO2 as a catalyst, Et4N[FeCl4] generates lower yields at wavelengths below about 380 nm, but higher yields at longer wavelengths. Selectivity for cyclohexanol is considerably greater with Et4N[FeCl4], and oxidation does not proceed past cyclohexanone.

Uniform and Gaussian UV Light Intensity Distribution on Droplet for Selective Area Deposition of Particles

2020 ◽  
Author(s):  
Tianyi Li ◽  
Aravinda Kar ◽  
Ranganathan Kumar
Keyword(s):  
Sessile Drop ◽  
Uv Light ◽  
Incident Light ◽  
Droplet Surface ◽  
Light Distribution ◽  
Surface Tension Gradient ◽  
Sharp Change ◽  
Sessile Droplet ◽  
Selective Area ◽  
Light Profiles

Abstract Particle transport through Marangoni convection inside a sessile droplet can be controlled by the UV light distribution on the surface. The photosensitive solution changes the surface tension gradient on the droplet surface and can induce clockwise and counter-clockwise circulations depending on the incident light distribution. In this paper, the stream function in the sessile drop has been evaluated in toroidal coordinates by solving the biharmonic equation. Multiple primary clockwise and counter-clockwise circulations are observed in the droplet under various concentric UV light profiles. The downward dividing streamlines are expected to deposit the particles on the substrate, thus matching the number of deposited rings on the substrate with the number of UV light rings. Moffatt eddies appear near the contact line or centerline of the droplet either due to a sharp change in the UV light profile or because the illuminated region is away from them.

scholarly journals Electrically-Tunable Blue Phase Liquid Crystal Microlens Array Based on a Photoconductive Film

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 65 ◽  
Author(s):  
Bing-Yau Huang ◽  
Shuan-Yu Huang ◽  
Chia-Hsien Chuang ◽  
Chie-Tong Kuo
Keyword(s):  
Refractive Index ◽  
Liquid Crystal ◽  
Electric Field ◽  
Uv Light ◽  
Focal Length ◽  
Incident Light ◽  
Microlens Array ◽  
Gradient Distribution ◽  
Phase Liquid ◽  
Blue Phase

This paper proposes an effective approach to fabricate a blue phase liquid crystal (BPLC) microlens array based on a photoconductive film. Owing to the characteristics of photo-induced conducting polymer polyvinylcarbazole (PVK), in which conductivity depends on the irradiation of UV light, a progressive mask resulting in the variation of conductivity is adopted to produce the gradient distribution of the electric field. The reorientations of liquid crystals according to the gradient distribution of the electric field induce the variation of the refractive index. Thus, the incident light experiences the gradient distribution of the refractive index and results in the focusing phenomenon. The study investigates the dependence of lens performance on UV exposure time, the focal length of the lens, and focusing intensities with various incident polarizations. The BPLC microlens array exhibits advantages such as electrically tunability, polarization independence, and fast response time.

scholarly journals Ferroelectric Induced UV Light-Responsive Memory Devices with Low Dark Current

Electronics ◽  
2021 ◽  
Vol 10 (16) ◽  
pp. 1897
Author(s):  
Hanleem Lee ◽  
Young Tea Chun
Keyword(s):  
Vinylidene Fluoride ◽  
Uv Light ◽  
Light Exposure ◽  
Incident Light ◽  
Colour Change ◽  
Memory Device ◽  
Interface Layer ◽  
Uv Illumination ◽  
Poly Vinylidene Fluoride ◽  
Stable Performance

We developed solution-processed hybrid photodetectors with a poly (9-vinylcarbazole)/zinc oxide nanoparticle photoactive layer and a poly (vinylidene fluoride-co-trifluoroethylene) ferroelectric copolymer buffer layer on flexible plastic substrates. The presence of a ferroelectric-poling interface layer significantly enhanced the charge transfer and responsivity of the photodetectors under ultraviolet (UV, 365 nm) light exposure. The responsivity of the device reached 250 mA/W at a reverse bias of 5 V and incident light intensity of 27.5 μW/cm2. This responsivity was four times higher than that of a device without the ferroelectric copolymer layer (64 mA/W) under the same conditions. The response time of the device to incident UV light also improved from 322 to 34 ms with the addition of the ferroelectric copolymer layer. In addition, the flexible device exhibited a stable performance in an air environment up to a maximum strain of 0.3 under bending stress. Finally, a UV-light-responsive memory device was successfully fabricated by using the developed hybrid photodetector and liquid crystals. This device showed a colour change from white to black upon UV illumination, and the on-state of the device was maintained for 30 s without light exposure owing to the polarization of poly (vinylidene fluoride-co-trifluoroethylene).

Uniform and Gaussian Ultraviolet Light Intensity Distribution on Droplet for Selective Area Deposition of Particles

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Tianyi Li ◽  
Aravinda Kar ◽  
Ranganathan Kumar
Keyword(s):  
Contact Line ◽  
Sessile Drop ◽  
Uv Light ◽  
Incident Light ◽  
Droplet Surface ◽  
Light Distribution ◽  
Surface Tension Gradient ◽  
Sessile Droplet ◽  
Selective Area ◽  
Light Profiles

Abstract Particle transport through Marangoni convection inside a sessile droplet can be controlled by the ultraviolet (UV) light distribution on the surface. The photosensitive solution changes the surface tension gradient on the droplet surface and can induce clockwise and counterclockwise circulations depending on the incident light distribution. In this paper, the stream function in the sessile drop has been evaluated in toroidal coordinates by solving the biharmonic equation. Multiple primary clockwise and counterclockwise circulations are observed in the droplet under various concentric UV light profiles. The downward dividing streamlines are expected to deposit the particles on the substrate, thus matching the number of deposited rings on the substrate with the number of UV light rings. Moffatt eddies appear near the contact line or centerline of the droplet depending on the UV light profile and its distance from the contact line.

scholarly journals Determination of Quantum Yield for the Photochemical Decomposition of Dichloramine-B and Dibromamine-B in Aqueous Acetic Acid Medium

2007 ◽  
Vol 4 (4) ◽  
pp. 502-509
Author(s):  
K. N. Mohana ◽  
N. Prasad ◽  
P. M. Ramadas Bhandarkar
Keyword(s):  
Acetic Acid ◽  
Quantum Yield ◽  
Uv Light ◽  
Incident Light ◽  
Aqueous Acetic Acid ◽  
Acetic Acid Medium ◽  
Rate Law ◽  
Photochemical Decomposition ◽  
Photolytic Decomposition

The photolysis of dihaloamines (RNX2),viz., dichloramine-B (DCB) and dibromamine-B (DBB) in aqueous acetic acid (1:1 v/v) solutions has been studied with the UV light source (λ= 2537 Å). The experimental rate law obtained is - d [RNX2] / dt = k' Io/ [RNX2], where Iois the intensity of incident light. The addition of benzenesulphonamide, the product of photolysis or uranyl ion had no significant effect on the rate of photochemical decomposition. A slight decrease in the rate has been observed by the addition of NaCl / NaBr to DCB / DBB solutions. The quantum yield (Φ) for the photolytic decomposition has been computed. A suitable photolytic mechanism and a rate law consistent with the observed results have been proposed.

scholarly journals Effect of ultraviolet light on the degradation of Low-Density and High-Density Polyethylene characterized by the weight loss and FTIR

2019 ◽  
Vol 1 (2) ◽  
pp. 26-31
Author(s):  
Prakash Bhuyar ◽  
Nurul Aqilah Binti Mohd Tamizi ◽  
Mohd Hasbi Ab. Rahim ◽  
Gaanty Pragas Maniam ◽  
Natanamurugaraj Govindan
Keyword(s):  
Weight Loss ◽  
High Density Polyethylene ◽  
Uv Light ◽  
Incident Light ◽  
Degradation Process ◽  
Sem Analysis ◽  
Ftir Spectrum ◽  
Physical Treatment ◽  
Photo Degradation ◽  
Vibrational Energies

In this study, the research was made to understand the knowledge widely related to the degradation process of polyethylene polymer. The mode of treatment that involves in the degradation process of polyethylene is physical treatment while the method of degradation used is photo-degradation of UV light. By using the physical treatment of UV irradiation light, it helps by affecting the bonding that holds the polymer together to break and weakens the plastic. From the result obtained in FTIR and SEM analysis, in FTIR spectrum of LDPE shows higher transmittance compared to FTIR spectrum of HDPE both UV-treated for 30 days. This indicates the high transmittance have few bonds to absorb light in the LDPE sample, low transmittance in HDPE sample means has high population of bonds which have vibrational energies corresponding to the incident light. For SEM result, the polyethylene for LDPE plastic sheet shows the best results for degradation and managed to reduce the weight loss at 87.5% compared to HDPE plastic which at 21.6%.

Holographic Photoetching of High-Quality Diffraction Gratings in P-GaAs for Distributed Feedback Lasers

1986 ◽  
Vol 75 ◽  
Author(s):  
Richard Matz
Keyword(s):  
Uv Light ◽  
Incident Light ◽  
Diffraction Gratings ◽  
Distributed Feedback ◽  
Distributed Feedback Lasers ◽  
High Quality

AbstractQuarter micrometer period diffraction gratings having depth-to-spacing ratios around 0.5 have been photochemically etched in p-GaAs using direct holographic illumination with 257 nm UV light. The results suggest the interaction of the incident light with the etched grating. The etch process is represented with the aid of a potential-pH diagram calculated from literature data.

scholarly journals High-Efficiency, Broadband, Near Diffraction-Limited, Dielectric Metalens in Ultraviolet Spectrum

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 490 ◽  
Author(s):  
Saima Kanwal ◽  
Jing Wen ◽  
Binbin Yu ◽  
Dileep Kumar ◽  
Xu Chen ◽  
...  
Keyword(s):  
High Efficiency ◽  
Uv Light ◽  
Incident Light ◽  
Optical Devices ◽  
Photonic Devices ◽  
Ultraviolet Spectrum ◽  
Optical Systems ◽  
Optical Components ◽  
Discrete Phase ◽  
Phase Accumulation

Ultraviolet (UV) optical devices have plenteous applications in the fields of nanofabrication, military, medical, sterilization, and others. Traditional optical components utilize gradual phase accumulation phenomena to alter the wave-front of the light, making them bulky, expensive, and inefficient. A dielectric metasurface could provide an auspicious approach to precisely control the amplitude, phase, and polarization of the incident light by abrupt, discrete phase changing with high efficiency due to low absorption losses. Metalenses, being one of the most attainable applications of metasurfaces, can extremely reduce the size and complexity of the optical systems. We present the design of a high-efficiency transmissive UV metalens operating in a broadband range of UV light (250–400 nm) with outstanding focusing characteristics. The polarization conversion efficiency of the nano-rod unit and the focusing efficiency of the metasurface are optimized to be as high as 96% and 77%, respectively. The off-axis focusing characteristics at different incident angles are also investigated. The designed metalens that is composed of silicon nitride nanorods will significantly uphold the advancement of UV photonic devices and can provide opportunities for the miniaturization and integration of the UV nanophotonics and its applications.

scholarly journals Method for Attaining Dimensionally Accurate Conditions for High-Resolution Three-Dimensional Printing Ceramic Composite Structures Using MicroCLIP Process

2019 ◽  
Vol 7 (3) ◽  
Author(s):  
Henry Oliver T. Ware ◽  
Cheng Sun
Keyword(s):  
High Resolution ◽  
Composite Structures ◽  
Uv Light ◽  
Incident Light ◽  
Three Dimensional ◽  
Building Blocks ◽  
Ceramic Particles ◽  
Traditional Manufacturing ◽  
Continuous Fabrication ◽  
Exposure Conditions

Continuous liquid interface production (CLIP) utilizes projection ultraviolet (UV) light and oxygen inhibition to transform the sequential layered three-dimensional (3D) manufacturing into a continuous fabrication flow with tremendous improved fabrication speed and structure integrity. Incorporating ceramic particles to the photo-curable polymers allows for additive manufacturing of ceramic parts featuring sophisticated geometries, mitigating the difficulties associated with traditional manufacturing processes. The presence of ceramic particles within the ink, however, strongly scatters the incident UV light. In the high-resolution CLIP (microCLIP) process, the scattering effect can significantly alter the process characteristics, resulting in broadening of lateral feature dimensions alongside curing depth reduction. Varying exposure conditions to accommodate scattering additionally affects the oxygen deadzone thickness (DZ), which is dependent on power of incident light. This introduces a systematic defocusing error for large deadzone thickness to further complicate process control, such as the unwanted narrowing of part features. In this work, we developed a systematic framework for process optimization by balancing those effects via experimental characterization. We showed that the reported method can provide a set of optimal process parameters (UV power and stage speed) for high-resolution 3D fabrication in accommodating the distinct characteristics of given photo-curable ceramic ink. The method to optimize process parameter was validated experimentally via fabricating a gradient index Luneburg lens comprising densely packed woodpile building-blocks with a strut width of 100 μm and a layer thickness of 60 μm using microCLIP at dimensionally accurate exposure conditions.

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