Effect Of Light Illumination Research Articles

Photo-catalytic polymerization of catechin molecules in alkaline aqueous

Polyphenols are associated with a wide range of physiological properties. Catechin is a flavan-3-ol with five phenolic hydroxyl groups. After blue light illumination, the transparent solution of catechin became yellowish. The effects of visible light illumination (400–800nm) were investigated on molecular structures and antioxidant capacities of catechin. Under the neutral or alkaline aqueous with the illumination of blue light, the photolysis and polymerization of catechin were observed in this study. A chromogenic catechin dimer was separated and identified as a proanthocyanidin by the chromatographic technique and mass spectrometry. For quantitative evaluation, the signal intensities of the catechin and the photochemical product show a negative correlation in the liquid chromatograms. The oligomer of flavan-3-ols (catechin dimer) is suggested as a dimeric B type proanthocyanidin, which has the molecular formula C30H26O12 and 578.14g/mol in exact mass. The mass spectrum of catechin dimer had characteristic ion signals in m/z 577, 560, 439Da. However, the total phenolic contents and scavenging O2− activity of catechin treated by blue light illumination are not changed significantly at the neutral or alkaline aqueous. Our results of photocatalytic oligomers of catechin provide a novel way to explain the sensory changes of green tea and a biochemical mechanism under the irradiation environments.

Optical Probe Ion and Carrier Dynamics at the CH3NH3PbI3 Interface with Electron and Hole Transport Materials

Ion migration and accumulation in perovskite and interface have recently attracted considerable research interest because it is closely related to carrier extraction and hence to the performance of perovskite solar cells. Here using specific optical probe techniques and perovskite, the authors investigate the effect of light illumination (soaking) at the CH3NH3PbI3/spiro‐OMeTAD and CH3NH3PbI3/Phenyl‐C61‐butyric‐acid‐methyl ester interfaces, focusing on the dynamics of mobile ions and photoexcited carriers. Time dependent photoluminescence (PL) intensity, electron–hole recombination and optical microscopy images are used to monitor the illumination effects at the interface as a function of light illumination time and intensity. Under continuous illumination, the PL intensity exhibits dynamic quenching in the timescale of seconds to minutes. The authors attribute this PL quenching to the accumulation of mobile ions at the interface during light soaking. Only negative ions cause such PL quenching and the rate at which PL intensity decreases depends on the illumination intensity. The authors found that the accumulated ions also impede the extraction of photogenerated holes from the perovskite layer into spiro‐OMeTAD, which increases electron–hole recombination. This investigation provides novel insight into the ion migration mechanism by light soaking and therefore its impact on the operation of a perovskite solar cell.

Controlling of DOS of TFTs based 6,13-bis(triisopropylsilylethynyl) pentacene by solar light illumination

The effect of dipole layer and white light illumination on the density of states for the 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) thin film transistor were investigated. We developed a physical compact model based on variable range hopping (VRH) theory for expressing the DOS in OTFTs that takes into account the effects of dipole layer and white light illumination. Using this model, we explain that the DOS for TIPS-pentacene thin film transistor depend strongly on the white light illumination under the surface dipole effect. Finally, an analytical model of drain-current has been developed in order to reproduce the output and transfer characteristics curves of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) phototransistor in saturation regime.

Mitigation of carbon dioxide by oleaginous microalgae for lipids and pigments production: Effect of light illumination and carbon dioxide feeding strategies

Oleaginous microalgae Nannochloropsis sp. was selected as potential strain for CO2 mitigation into lipids and pigments. The synergistic effects of light intensity and photoperiod were evaluated to provide the adequate light energy for this strain. The saturation light intensity was 60μmol·photon·m−2s−1. With full illumination, the biomass obtained was 0.850±0.16g·L−1 with a lipid content of 44.7±1.2%. The pigments content increased with increasing light energy supply. Three main operating factors including initial cell concentration, CO2 content and gas flow rate were optimized through Response Surface Methodology. The feedings with low CO2 content at high gas flow rate gave the maximum biomass but with low lipid content. After optimization, the biomass and lipid production were increased up to 1.30±0.103g·L−1 and 0.515±0.010g·L−1, respectively. The CO2 fixation rate was as high as 0.729±0.04g·L−1d−1. The fatty acids of Nannochloropsis sp. lipids were mainly C16-C18 indicating its potential use as biodiesel feedstocks.

The role of graphene formed on silver nanowire transparent conductive electrode in ultra-violet light emitting diodes.

This paper reports a highly reliable transparent conductive electrode (TCE) that integrates silver nanowires (AgNWs) and high-quality graphene as a protecting layer. Graphene with minimized defects and large graphene domains has been successfully obtained through a facile two-step growth approach. Ultraviolet light emitting diodes (UV-LEDs) were fabricated with AgNWs or hybrid electrodes where AgNWs were combined with two-step grown graphene (A-2GE) or conventional one-step grown graphene (A-1GE). The device performance and reliability of the UV-LEDs with three different electrodes were compared. The A-2GE offered high figure of merit owing to the excellent UV transmittance and reduced sheet resistance. As a consequence, the UV-LEDs made with A-2GE demonstrated reduced forward voltage, enhanced electroluminescence (EL) intensity, and alleviated efficiency droop. The effects of joule heating and UV light illumination on the electrode stability were also studied. The present findings prove superior performance of the A-2GE under high current injection and continuous operation of UV LED, compared to other electrodes. From our observation, the A-2GE would be a reliable TCE for high power UV-LEDs.

Illumination Effect on Bipolar Switching Properties of Gd:SiO2 RRAM Devices Using Transparent Indium Tin Oxide Electrode.

To discuss the optoelectronic effect on resistive random access memory (RRAM) devices, the bipolar switching properties and electron-hole pair generation behavior in the transparent indium tin oxide (ITO) electrode of Gd:SiO2 thin films under the ultraviolet (λ = 400 nm) and red-light (λ = 770 nm) illumination for high resistance state (HRS)/low resistance state (LRS) was observed and investigated. In dark environment, the Gd:SiO2 RRAM devices exhibited the ohmic conduction mechanism for LRS, exhibited the Schottky emission conduction and Poole-Frankel conduction mechanism for HRS. For light illumination effect, the operation current of the Gd:SiO2 RRAM devices for HRS/LRS was slightly increased. Finally, the electron-hole pair transport mechanism, switching conduction diagram, and energy band of the RRAM devices will be clearly demonstrated and explained.

Cross-Sectional Investigations on Epitaxial Silicon Solar Cells by Kelvin and Conducting Probe Atomic Force Microscopy: Effect of Illumination.

Both surface photovoltage and photocurrent enable to assess the effect of visible light illumination on the electrical behavior of a solar cell. We report on photovoltage and photocurrent measurements with nanometer scale resolution performed on the cross section of an epitaxial crystalline silicon solar cell, using respectively Kelvin probe force microscopy and conducting probe atomic force microscopy. Even though two different setups are used, the scans were performed on locations within 100-μm distance in order to compare data from the same area and provide a consistent interpretation. In both measurements, modifications under illumination are observed in accordance with the theory of PIN junctions. Moreover, an unintentional doping during the deposition of the epitaxial silicon intrinsic layer in the solar cell is suggested from the comparison between photovoltage and photocurrent measurements.

Mass spectral study of storage conditions and paper substrates on the degradation and analytical sensitivity of therapeutic drugs in dried blood spots

Dried blood spot sampling technique has been a prevalent approach in therapeutic drug monitoring due to its numerous advantages over conventional blood or plasma sampling. But the effects of storage conditions, drying time in air and paper substrates on the stability and analysis sensitivity of therapeutic drugs are still lack. Herein we systematically investigated the effects of storage conditions and paper substrates on the appearance of dried blood spots and stability of different therapeutic drugs by using a facile paper spray mass spectrometry. The results demonstrated using silica coated paper SG81 favored to get an abundant signal due to the unique elution behavior of target compounds in dried blood spots relative to that with grade ET31 and grade 1 paper substrates. By examining the effects of light illumination and air on the stability of therapeutic drug, it reveals that both have a similar impact on the degradation of the tested drugs, whereas storing the samples in a zip-foiled bag could effectively suppress the degradation of the analytes in dried blood. The analysis sensitivity of different drugs in blood samples was also compared under different storage conditions. An improvement of 2–10-fold analysis sensitivity was obtained for these drugs when the DBS were stored in a zip-foiled bag relative to that exposure to air.

Effect of Light Illumination on Leaves Movement of <i>Mimosa pudica</i>

A study on the effect of light illumination introduced to the leaves of Mimosa pudica was carried out using different light intensities. The leaves will open gradually from the closed condition after the light was illuminated. Plant of M. pudica was placed in the dark box during measurement meanwhile the Petiole (part of the stem) of the plant was at normal position (hanging up). The camera was fixed to the box to monitor the leaves’ movement continuous and real time. By using this method the change of the top view area of the leaves could be observed. A crossed line was drawn on the image recorded and was measured its length. The calculation of the length gives the percentage of leaves at open during the observation time. Ultrasonic apparatus was also used to monitor the change of leaves. From the results, at an illumination intensity of 200 Lux, the percentage of leaves to open completely with respects to the observation time was found to increase nonlinearly by taking the time of 25 minutes. For intensities of 400 Lux, the trend of curve was also similar but increase rapidly. The ultrasonic signals show much stable at 200 Lux comparing to 400 Lux that was fluctuating. That may be due to the relatively faster movement of the leaves to open. This natural phenomenon is interesting and may introduce any change of natural indication that could be explored for further applications.

Rifampicin adsorbed onto magnetite nanoparticle: SERS study and insight on the molecular arrangement and light effect

In this study, the surface‐enhanced Raman spectroscopy (SERS) technique was used to asses key information regarding the surface adsorption of Rifampicin (RIF) onto magnetite nanoparticle previously dressed with a bilayer of lauric acid (LA). The effects of white light illumination on the physicochemical properties of the RIF molecule were also investigated. Transmission electron microscopy, dynamic light scattering, zeta‐potential, and Fourier transform infrared spectroscopy were also employed to characterize the investigated materials. Vibrational mode assignments for the SERS spectra and comparison between the data recorded from the free and adsorbed RIF provided insights for the adsorption of this biomolecule onto the LA‐bilayer dressed magnetite nanoparticle. The results suggested that the species binding to the outer carboxylate group of the LA‐bilayer is more likely the piperazine nitrogen adjacent to the imine nitrogen. The SERS data also revealed the enhancement of the RIF molecule stability to white light irradiation while adsorbed onto the magnetite nanoparticle. Copyright © 2015 John Wiley & Sons, Ltd.

Electrical investigation of TiO2 thin films coated on glass and silicon substrates—effect of UV and visible light illumination

The conducting nature of nanocrystalline TiO2 thin film coated on glass and silicon (Si) substrates was studied in detail. The films were prepared through sol–gel spin-coating method with variation in coating parameters viz, the thickness of the film and the post annealing temperature. The thickness of the films was measured using Stylus profilometer. The resistivity of the film, as a function of film thickness, under the illumination of UV, visible light, and dark conditions was found using the four-probe method. The results show that the resistivity of the film decreases with increase in thickness of the film. The decrease in resistivity of the film is attributed to increase in cross-sectional area and rearrangement and removal of defects. Illumination of the samples under visible and UV light further decreases the resistivity of the film. The electrical resistivity of TiO2 film coated on Si substrate was observed to be lesser than that of the glass substrate.

The Stability of Noise Behavior in Amorphous Indium Gallium Zinc Oxide Thin Film Transistors under Illumination

In this paper, the effects of light illumination on the noise are rarely discussed. In order to find out the noise behavior of a-IGZO TFTs under light and its change owing to the induced instability, we investigate the noise spectrum density of the a-IGZO TFTs under illumination conditions.

Intriguing photo-control of exchange bias in BiFeO3/La2/3Sr1/3MnO3 thin films on SrTiO3 substrates

To date, electric fields have been widely used to control the magnetic properties of BiFeO3-based antiferromagnet/ferromagnet heterostructures through application of an exchange bias. To extend the applicability of exchange bias, however, an alternative mechanism to electric fields is required. Here, we report the photo-control of exchange bias in BiFeO3/La2/3Sr1/3MnO3 thin films on an SrTiO3 substrate. Through an ex situ pulsed laser deposition technique, we successfully synthesized epitaxial BiFeO3/La2/3Sr1/3MnO3 thin films on SrTiO3 substrates. By measuring magnetoresistance under light illumination, we investigated the effect of light illumination on resistance, exchange bias, and coercive field in BiFeO3/La2/3Sr1/3MnO3 thin films. After illumination of red and blue lights, the exchange bias was sharply reduced compared to that measured in the dark. With increasing light intensity, the exchange bias under red and blue lights initially decreased to zero and then appeared again. It is possible to reasonably explain these behaviors by considering photo-injection from SrTiO3 and the photo-conductivity of La2/3Sr1/3MnO3. This study may provide a fundamental understanding of the mechanism underlying photo-controlled exchange bias, which is significant for the development of new functional spintronic devices.

Optical pumping of deep traps in AlGaN/GaN-on-Si HEMTs using an on-chip Schottky-on-heterojunction light-emitting diode

In this work, by using an on-chip integrated Schottky-on-heterojunction light-emitting diode (SoH-LED) which is seamlessly integrated with the AlGaN/GaN high electron mobility transistor (HEMT), we studied the effect of on-chip light illumination on the de-trapping processes of electrons from both surface and bulk traps. Surface trapping was generated by applying OFF-state drain bias stress, while bulk trapping was generated by applying positive substrate bias stress. The de-trapping processes of surface and/or bulk traps were monitored by measuring the recovery of dynamic on-resistance Ron and/or threshold voltage Vth of the HEMT. The results show that the recovery processes of both dynamic Ron and threshold voltage Vth of the HEMT can be accelerated by the on-chip SoH-LED light illumination, demonstrating the potentiality of on-chip hybrid opto-HEMTs to minimize the influences of traps during dynamic operation of AlGaN/GaN power HEMTs.

Femtosecond laser-fabricated biochip for studying symbiosis between Phormidium and seedling root

We present the fabrication of a waveguide-like structure in a polydimethylsiloxane (PDMS) polymer substrate using a femtosecond laser to study the mechanism of symbiosis between filamentous cyanobacteria, Phormidium, and a seedling root. While symbiosis occurring underground promotes the growth of vegetable seedlings, the details of the mechanism remain unclear. Understanding the mechanisms of Phormidium gliding to the seedling root will facilitate improving the mat formation of Phormidium, which will lead to increased vegetable production. We assumed a symbiosis mechanism in which sunlight propagates through the seedling root and is scattered underground to guide the Phormidium gliding. Once attached to the root, Phormidium uses the scattered light for photosynthesis. Photosynthetic products, in turn, promote an increase in Phormidium mat formation and vegetable growth. To verify this assumption, the optical characteristics of the seedling root were investigated. A waveguide-like structure with the same optical characteristics of the root was subsequently fabricated by femtosecond laser in PDMS polymer to assess the light illumination effect on Phormidium behavior.

Catalytic effect of light illumination on bioleaching of chalcopyrite

The influence of visible light exposure on chalcopyrite bioleaching was investigated using Acidithiobacillus ferrooxidans. The results indicated, in both shake-flasks and aerated reactors with 8500-lux light, the dissolved Cu was 91.80% and 23.71% higher, respectively, than that in the controls without light. The catalytic effect was found to increase bioleaching to a certain limit, then plateaued as the initial chalcopyrite concentration increased from 2% to 4.5%. Thus a balanced mineral concentration is highly amenable to bioleaching via offering increased available active sites for light adsorption while eschewing mineral aggregation and screening effects. Using semiconducting chalcopyrite, the light facilitated the reduction of Fe3+ to Fe2+ as metabolic substrates for A.ferrooxidans, leading to better biomass, lower pH and redox potential, which are conducive to chalcopyrite leaching. The light exposure on iron redox cycling was further confirmed by chemical leaching tests using Fe3+, which exhibited higher Fe2+ levels in the light-induced system.

Effects of light illumination on electron velocity of AlGaN/GaN heterostructures under high electric field

We have investigated the variation of electron velocity in AlGaN/GaN heterostructures depending on illuminating light intensity and wavelength. It is shown that the electron velocity at high electric field increases under above-band light illumination. This electron velocity enhancement is found to be related to the photo-generated cold holes which interact with hot electrons and thus accelerate the energy relaxation at high electric field. The results suggest an alternative way to improve the electron energy relaxation rate and hence the electron velocity in GaN based heterostructures.

Implantable photonic devices for improved medical treatments.

An evolving area of biomedical research is related to the creation of implantable units that provide various possibilities for imaging, measurement, and the monitoring of a wide range of diseases and intrabody phototherapy. The units can be autonomic or built-in in some kind of clinically applicable implants. Because of specific working conditions in the live body, such implants must have a number of features requiring further development. This topic can cause wide interest among developers of optical, mechanical, and electronic solutions in biomedicine. We introduce preliminary clinical trials obtained with an implantable pill and devices that we have developed. The pill and devices are capable of applying in-body phototherapy, low-level laser therapy, blue light (450 nm) for sterilization, and controlled injection of chemicals. The pill is also capable of communicating with an external control box, including the transmission of images from inside the patient’s body. In this work, our pill was utilized for illumination of the sinus-carotid zone in dog and red light influence on arterial pressure and heart rate was demonstrated. Intrabody liver tissue laser ablation and nanoparticle-assisted laser ablation was investigated. Sterilization effect of intrabody blue light illumination was applied during a maxillofacial phlegmon treatment.

Optogenetics, the intersection between physics and neuroscience: light stimulation of neurons in physiological conditions.

Neuronal stimulation by light is a novel approach in the emerging field of optogenetics, where genetic engineering is used to introduce light-activated channels. However, light is also capable of stimulating neurons even in the absence of genetic modifications through a range of physical and biological mechanisms. As a result, rigorous design of optogenetic experiments needs to take note of alternative and parallel effects of light illumination of neuronal tissues. Thus all matters relating to light penetration are critical to the development of studies using light-activated proteins. This paper discusses ways to quantify light, light penetration in tissue, as well as light stimulation of neurons in physiological conditions. We also describe the direct effect of light on neurons investigated at different sites.

Flash Lamp Annealing Effect on Stability of Oxide TFT

Flash-lamp annealing (FLA) of a millisecond time scale has been shown to be a promising tool in the preparation of high-quality semiconducting materials. The flash lamp anneal pulse width is so small that thermal stresses becomes small. A combined thermal and optical model has been developed to predict the substrate temperature distribution and this model is related to a structural model to compute stresses and deflections. We used flash-lamp annealing to improve the quality of oxide material for the TFT application. We investigated the flash lamp annealing to improve the stability of Oxide TFT. The IGZO (Indium Gallium Zinc Oxide) was deposited on a glass for the characterization of a single layer. And next, The Oxide TFT was fabricated on the P-type wafer with thermal SiO2 of 3000 Ǻ. The IGZO was deposited on the substrate by the RF Sputter. And then, the sample was annealed at 430 ℃ in a furnace. We have investigated Xenon (Xe) FLA effect on the stability of each IGZO single layer and Oxide TFT. We investigated the effect of the FLA as varying the power of the lamp. And also, we investigated the effect of the substrate temperature and shot numbers of the flash lamp. A metal layer for source and drain electrode was deposited after FLA by the thermal evaporation. We measured the bias stress and light illumination effect on the transfer curves. For the structural analysis, we used the Raman spectroscopy, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS).