International Journal of Photoenergy The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Effect of Ce Doping on RGO-TiO2 Nanocomposite for High Photoelectrocatalytic Behavior Tue, 15 Apr 2014 14:04:46 +0000 Ce doped RGO-TiO2 composite films on ITO substrates were prepared by sol-gel process using tetrabutyl titanate and reduced graphene oxide (RGO) as the starting materials. The sample was designed for the photoelectrocatalytic applications. The obtained samples were characterized by X-ray diffraction, UV-vis absorption spectroscopy, scanning electron microscopy, and Fourier transformed infrared spectroscopy. The results showed that doping of Ce on RGO-TiO2 composite film inhibited the TiO2 anatase-rutile phase transformation. In this case, Ce atoms could serve as dispersion oxide and suppress the recombination of photoinduced electron-hole pairs. Besides, the change in absorbance from UV to visible region was observed in Ce doped RGO-TiO2 nanocomposite films. The Ce doped RGO-TiO2 composite film showed higher photoelectrochemical performance than that of RGO-TiO2 composite and pure TiO2 under solar simulator irradiation. The main reason might be attributed to the optimum content of Ce that could act as electrons acceptor to hinder the recombination loss and facilitate the better transportation for photoinduced charge carriers. Md. Rakibul Hasan, Chin Wei Lai, Sharifah Bee Abd Hamid, and Wan Jeffrey Basirun Copyright © 2014 Md. Rakibul Hasan et al. All rights reserved. Reconfigurable Charge Pump Circuit with Variable Pumping Frequency Scheme for Harvesting Solar Energy under Various Sunlight Intensities Tue, 15 Apr 2014 09:08:02 +0000 We propose variable pumping frequency (VPF) scheme which is merged with the previous reconfigurable charge pump (RCP) circuit that can change its architecture according to a given sunlight condition. Here, merging the VPF scheme with the architecture reconfiguration can improve percentage output currents better by 21.4% and 22.4% than RCP circuit with the fixed pumping frequencies of 7 MHz and 15 MHz, respectively. Comparing the VPF scheme with real maximum power points (MPP), the VPF can deliver 91.9% of the maximum amount of output current to the load on average. In terms of the power and area overheads, the VPF scheme proposed in this paper consumes the power by 0.4% of the total power consumption and occupies the layout area by 1.61% of the total layout area. Jeong Heon Kim, Sang Don Byeon, Hyun-Sun Mo, and Kyeong-Sik Min Copyright © 2014 Jeong Heon Kim et al. All rights reserved. Improved Synthesis of Reduced Graphene Oxide-Titanium Dioxide Composite with Highly Exposed 001 Facets and Its Photoelectrochemical Response Mon, 14 Apr 2014 16:01:49 +0000 Crystal facet engineering has attracted worldwide attention, particularly in facet manipulation of titanium dioxide (TiO2) surface properties. An improved synthesis by solvothermal route has been employed for the formation of TiO2 with highly exposed facets decorated on reduced graphene oxide (RGO) sheets. The RGO-TiO2 composite could be produced with high yield by following a stringently methodical yet simple approach. Field emission scanning electron microscope and high resolution transmission electron microscope imaging reveal that the structure consists of TiO2 nanoparticles covered with TiO2 nanosheets of exposed facets on a RGO sheet. The photocurrent response of the RGO-TiO2 composite was discovered to outperform that of pure TiO2, as a ~10-fold increase in photocurrent density was observed for the RGO-TiO2 electrodes. This may be attributed to rapid electron transport and the delayed recombination of electron-hole pairs due to improved ionic interaction between titanium and carbon. Gregory S. H. Thien, Fatin Saiha Omar, Nur Ily Syuhada Ahmad Blya, Wee Siong Chiu, Hong Ngee Lim, Ramin Yousefi, Farid-Jamali Sheini, and Nay Ming Huang Copyright © 2014 Gregory S. H. Thien et al. All rights reserved. Optical and Electrical Effects of p-type μc-SiOx:H in Thin-Film Silicon Solar Cells on Various Front Textures Mon, 14 Apr 2014 12:13:56 +0000 p-type hydrogenated microcrystalline silicon oxide (µc-Si:H) was developed and implemented as a contact layer in hydrogenated amorphous silicon (a-Si:H) single junction solar cells. Higher transparency, sufficient electrical conductivity, low ohmic contact to sputtered ZnO:Al, and tunable refractive index make p-type µc-Si:H a promising alternative to the commonly used p-type hydrogenated microcrystalline silicon (µc-Si:H) contact layers. In this work, p-type µc-Si:H layers were fabricated with a conductivity of up to 10−2 S/cm and a Raman crystallinity of above 60%. Furthermore, we present p-type µc-Si:H films with a broad range of optical properties (2.1 eV < band gap  eV and 1.6 < refractive index ). These properties can be tuned by adapting deposition parameters, for example, the CO2/SiH4 deposition gas ratio. A conversion efficiency improvement of a-Si:H solar cells is achieved by applying p-type µc-Si:H contact layer compared to the standard p-type µc-Si:H contact layer. As another aspect, the influence of the front side texture on a-Si:H p-i-n solar cells with different p-type contact layers, µc-Si:H and µc-Si:H, is investigated. Furthermore, we discuss the correlation between the decrease of and the cell surface area derived from AFM measurements. Chao Zhang, Matthias Meier, Andreas Lambertz, Vladimir Smirnov, Bernhard Holländer, Aad Gordijn, and Tsvetelina Merdzhanova Copyright © 2014 Chao Zhang et al. All rights reserved. Synthesis and Photocatalytic Activity of Magnetically Recoverable Core-Shell Nanoparticles Mon, 14 Apr 2014 08:57:30 +0000 TiO2/SiO2/Fe3O4 (TSF) core-shell nanoparticles with good photocatalytic activity that are capable of fast magnetic separation have been successfully prepared by chemical coprecipitation and two-step sol-gel process. The as-prepared TSF nanoparticles were calcined at high temperature in order to transform the amorphous titanium dioxide into a photoactive crystalline phase. The calcined nanoparticles are composed of a Fe3O4 core with a strong response to external magnetic fields, a SiO2 intermediary layer, and a TiO2 outshell. Vibration sample magnetometer (VSM) analysis confirms the superparamagnetism of calcined nanoparticles, which can enhance the recoverable properties of the novel photocatalyst. When the TiO2/SiO2/Fe3O4 core-shell nanoparticles are added to the crude oily wastewater, they exhibit high photocatalytic activity in the degradation of crude oily wastewater. The oil concentration could be reduced to lower than 30 ppm within 20 minutes for the case of initial oil concentration less than 350 ppm. It has been found that the TSF nanoparticles could be easily separated from the wastewater and withdrawn by using an external magnetic field. The recovered TSF nanoparticles possess high efficiency in the degradation of crude oily wastewater even after three times successive reuse. The present results indicate that TSF core-shell nanoparticles possess great application perspectives in the degradation of crude oily wastewater. Zhen Peng, Hua Tang, Yao Tang, Ke Fu Yao, and Hong Hong Shao Copyright © 2014 Zhen Peng et al. All rights reserved. Hole-Phonon Relaxation and Photocatalytic Properties of Titanium Dioxide and Zinc Oxide: First-Principles Approach Mon, 14 Apr 2014 08:25:29 +0000 First-principles calculations for the temporal characteristics of hole-phonon relaxation in the valence band of titanium dioxide and zinc oxide have been performed. A first-principles method for the calculations of the quasistationary distribution function of holes has been developed. The results show that the quasistationary distribution of the holes in TiO2 extends to an energy level approximately 1 eV below the top of the valence band. This conclusion in turn helps to elucidate the origin of the spectral dependence of the photocatalytic activity of TiO2. Analysis of the analogous data for ZnO shows that in this material spectral dependence of photocatalytic activity in the oxidative reactions is unlikely. V. P. Zhukov, V. G. Tyuterev, E. V. Chulkov, and P. M. Echenique Copyright © 2014 V. P. Zhukov et al. All rights reserved. Long Wavelength Plasmonic Absorption Enhancement in Silicon Using Optical Lithography Compatible Core-Shell-Type Nanowires Thu, 10 Apr 2014 14:13:29 +0000 Plasmonic properties of rectangular core-shell type nanowires embedded in thin film silicon solar cell structure were characterized using FDTD simulations. Plasmon resonance of these nanowires showed tunability from  nm to  nm with variation of dimensional parameters within the feature resolution specifications of Deep Ultraviolet and Laser Interference Lithography techniques. A half-shell nanowire structure was proposed for simplifying device integration which showed 10 times absorption enhancement in silicon at  nm. However this absorption was significantly smaller than the Ohmic loss in the silver shell due to very low near-bandgap absorption properties of silicon. Prospect of improving enhanced absorption in silicon to Ohmic loss ratio by utilizing dual capability of these nanowires in boosting impurity photovoltaic effect and efficient extraction of the photogenerated carriers was discussed. Our results indicate that high volume fabrication capacity of optical lithography techniques can be utilized for plasmonic absorption enhancement in thin film silicon solar cells over the entire long wavelength range of solar radiation. Mohammed Shahriar Sabuktagin, Khairus Syifa Hamdan, Khaulah Sulaiman, Rozalina Zakaria, and Harith Ahmad Copyright © 2014 Mohammed Shahriar Sabuktagin et al. All rights reserved. Optimization of p-GaN/InGaN/n-GaN Double Heterojunction p-i-n Solar Cell for High Efficiency: Simulation Approach Thu, 10 Apr 2014 11:39:55 +0000 We have conducted numerical simulation of p-GaN/In0.12Ga0.88N/n-GaN, p-i-n double heterojunction solar cell. The doping density, individual layer thickness, and contact pattern of the device are investigated under solar irradiance of AM1.5 for optimized performance of solar cell. The optimized solar cell characteristic parameters for cell area of 1  × 1 mm2 are open circuit voltage of 2.26 V, short circuit current density of 3.31 mA/cm2, fill factor of 84.6%, and efficiency of 6.43% with interdigitated grid pattern. Aniruddha Singh Kushwaha, Pramila Mahala, and Chenna Dhanavantri Copyright © 2014 Aniruddha Singh Kushwaha et al. All rights reserved. Superior Antireflection Coating for a Silicon Cell with a Micronanohybrid Structure Thu, 10 Apr 2014 07:11:47 +0000 The object of this paper is to develop a high antireflection silicon solar cell. A novel two-stage metal-assisted etching (MAE) method is proposed for the fabrication of an antireflective layer of a micronanohybrid structure array. The processing time for the etching on an N-type high-resistance (NH) silicon wafer can be controlled to around 5 min. The resulting micronanohybrid structure array can achieve an average reflectivity of 1.21% for a light spectrum of 200–1000 nm. A P-N junction on the fabricated micronanohybrid structure array is formed using a low-cost liquid diffusion source. A high antireflection silicon solar cell with an average efficiency of 13.1% can be achieved. Compared with a conventional pyramid structure solar cell, the shorted circuit current of the proposed solar cell is increased by 73%. The major advantage of the two-stage MAE process is that a high antireflective silicon substrate can be fabricated cost-effectively in a relatively short time. The proposed method is feasible for the mass production of low-cost solar cells. Hsi-Chien Liu and Gou-Jen Wang Copyright © 2014 Hsi-Chien Liu and Gou-Jen Wang. All rights reserved. Assessment of the Operating Temperature of Crystalline PV Modules Based on Real Use Conditions Thu, 10 Apr 2014 00:00:00 +0000 Determining the operating temperature of photovoltaic panels is important in evaluating the actual performance of these systems. In the literature, different correlations exist, in either explicit or implicit forms, which often do not account for the electrical behaviour of panels; in this way, estimating is based only on the passive behaviour of the . In this paper, the authors propose a new implicit correlation that takes into account the standard weather variables and the electricity production regimes of a panel in terms of the proximity to the maximum power points. To validate its reliability, the new correlation was tested on two different PV panels (Sanyo and Kyocera panels) and the results were compared with values obtained from other common correlations already available in the literature. The data show that the quality of the new correlation drastically improves the estimation of the photovoltaic operating temperature. Giuseppina Ciulla, Valerio Lo Brano, Vincenzo Franzitta, and Marco Trapanese Copyright © 2014 Giuseppina Ciulla et al. All rights reserved. Growth of Anodic Aluminum Oxide Templates and the Application in Fabrication of the BiSbTe-Based Thermoelectric Nanowires Wed, 09 Apr 2014 12:32:47 +0000 A two-step electrochemical anodization was used to form the anodic aluminum oxide (AAO) thin films with nanotube arrays of self-organized honeycomb structure. Al foil was anodized in 10% sulfuric acid (H2SO4) and 3% oxalic acid (H2C2O4) at 25°C at constant voltage of 40 V for 60 min for two times. Ethylene glycol (C2H6O2) was used as a solution and 0.3 M potassium iodide (KI) was used to improve the solution’s conductivity. Different electrolyte concentrations of Bi(NO3)3-5H2O, SbCl3, and TeCl4 were added into KI-C2H6O2 solution and the cyclic voltammetry experiment was used to find the reduced voltages of Bi3+, Sb3+, and Te4+ ions. The potentiostatic deposition and pulse electrodeposition (PED) processes were used to deposit the (Bi,Sb)2−xTe3+x-based materials. Field-emission scanning electron microscope and energy dispersive spectrometers were used to analyze the compositions of the deposited (Bi,Sb)2−xTe3+x-based materials. After finding the optimal deposition parameter of the PED process the AAO nanotube arrays were used as the templates to deposit the (Bi,Sb)2−xTe3+x-based thermoelectric nanowires. Chin-Guo Kuo, Yuan-Tai Hsieh, Cheng-Fu Yang, Ching-Ho Huang, and Chia-Ying Yen Copyright © 2014 Chin-Guo Kuo et al. All rights reserved. Investigation Performance and Mechanisms of Inverted Polymer Solar Cells by Pentacene Doped P3HT : PCBM Tue, 08 Apr 2014 08:52:27 +0000 The inverted polymer solar cells (PSCs) with pentacene-doped P3HT : PCBM absorption layers were fabricated. It was demonstrated that the pentacene doping modulated the electron mobility and the hole mobility in the resulting absorption layer. Furthermore, by varying the doping content, the optimal carrier mobility balance could be obtained. In addition, the pentacene doping led to an improvement in the crystallinity of the resulting films and made an enhancement in the light absorption, which was partly responsible for the performance improvement of the solar cells. Using the space-charge-limited current (SCLC) method, it was determined that the balanced carrier mobility () was nearly achieved when a pentacene doping ratio of 0.065 by weight was doped into the P3HT : PCBM : pentacene absorption layer. Compared with the inverted PSCs without the pentacene doping, the short circuit current density and the power conversion efficiency of the inverted PSCs with the pentacene doping ratio of 0.065 were increased from 9.73 mA/cm2 to 11.26 mA/cm2 and from 3.39% to 4.31%, respectively. Hsin-Ying Lee and Hung-Lin Huang Copyright © 2014 Hsin-Ying Lee and Hung-Lin Huang. All rights reserved. Au-Loaded Titanium Dioxide Nanoparticles Synthesized by Modified Sol-Gel/Impregnation Methods and Their Application to Dye-Sensitized Solar Cells Mon, 07 Apr 2014 16:37:26 +0000 Au-loaded TiO2 nanoparticles were synthesized by the modified sol-gel method together with the impregnation method. Anatase phase of TiO2 was obtained in all samples with an average particle size of 20 nm. For the enhancement of DSSCs, the dye-sensitized solar cells composed of the ITO/Au-loaded TiO2/N-719/electrolyte/Pt were fabricated. Au-loaded TiO2 films were deposited by using squeegee method. Finally, the fabricated cells were studied upon an irradiation of solar light to study the performance. The fabricated cell with up to 1.0 mol% Au-loaded TiO2 could enhance the performance by localized surface plasmon effect and scattering property. Hathaithip Ninsonti, Weerasak Chomkitichai, Akira Baba, Natda Wetchakun, Wiyong Kangwansupamonkon, Sukon Phanichphant, Kazunari Shinbo, Keizo Kato, and Futao Kaneko Copyright © 2014 Hathaithip Ninsonti et al. All rights reserved. The Influence of Hydrogen on the Properties of Zinc Sulfide Thin Films Deposited by Magnetron Sputtering Mon, 07 Apr 2014 13:47:46 +0000 Zinc sulfide thin films have been deposited with hydrogen in Ar and Ar+H2 atmosphere by radio frequency magnetron sputtering. The thickness, structural properties, composition, surface morphology, and optical and electrical properties of the films have been investigated. Effect of hydrogen on the properties of the film was studied. The results showed that hydrogen leads to better crystallinity and larger crystallite size of ZnS polycrystalline films. The band gaps of the films in Ar+H2 are about 3.48 eV compared with 3.24 eV without hydrogen. It is also demonstrated that hydrogen can result in a better stoichiometric composition of the films. Hang Xu, Lili Wu, Wenwu Wang, Lixiang Zhang, Jingquan Zhang, Wei Li, and Lianghuan Feng Copyright © 2014 Hang Xu et al. All rights reserved. Inhibitory Effects of 658 nm Laser Irradiation on Skin Temperature in Anesthetized Rats: Preliminary Results from a Controlled Study Mon, 07 Apr 2014 13:36:28 +0000 Red laser light stimulation can have many physiological effects. The goal of this animal experimental study was to investigate how red laser stimulation influences the temperature of anesthetized rats at different acupuncture points and nonacupoints. For that reason 12 adult male Wistar Han rats (300–380 g) were investigated. Six anesthetized rats underwent red laser stimulation (wavelength 658 nm, output power 40 mW, diameter 500 µm, and duration 10 min) at the Baihui (GV20) acupoint, the Zusanli acupoint (ST36, bilateral), and a control point on the forelimb. The other six rats underwent the same procedure; however, the laser remained switched off. Significant decreases in temperature were found at the acupoints Baihui, Zusanli left, and Zusanli right. In addition there was no significant temperature effect at a control point. During placebo laser irradiation (deactivated laser) there were also significant temperature changes. The mechanism underlying the results is currently unknown, but brain stimulation (via laser or mechanical pressure) and mainly direct central mechanisms may be responsible for the local and peripheral temperature decrease. Daniela Litscher, Xiaoyu Wang, Miriam Schneider, Chris M. Friemel, and Gerhard Litscher Copyright © 2014 Daniela Litscher et al. All rights reserved. Noncompensated Codoping TiO2 Nanowires: The Enhanced Visible Light Photocatalytic Properties Mon, 07 Apr 2014 13:20:19 +0000 The codoped nanowire samples are prepared by hydro-thermal method and annealed in NH3 atmosphere. The XRD (X-ray diffraction), SEM (Scanning electron microscope), UV-vis absorption spectroscopy, and BET (Brunauer, Emmett, and Teller) results indicate that the samples are pure anatase nanowires. The codoped samples have the highest specific surface area, the largest red-shift, and the largest absorption enhancement in the visible light range compared with Fe doped, N doped, and undoped nanowires. The measurements of XPS (X-ray photoelectron spectroscopy) show that N content of codoped TiO2 is about two times as large as that of the N doped TiO2. It is assumed that nitrogen doping plays a very important role for the photocatalytic activity increase and hence the codoped nanowire TiO2 shows the most effective photocatalytic activity under the visible light irradiation. Zhongpo Zhou and Haiying Wang Copyright © 2014 Zhongpo Zhou and Haiying Wang. All rights reserved. Buck-Boost/Forward Hybrid Converter for PV Energy Conversion Applications Mon, 07 Apr 2014 00:00:00 +0000 This paper presents a charger and LED lighting (discharger) hybrid system with a PV array as its power source for electronic sign indicator applications. The charger adopts buck-boost converter which is operated in constant current mode to charge lead-acid battery and with the perturb and observe method to extract maximum power of PV arrays. Their control algorithms are implemented by microcontroller. Moreover, forward converter with active clamp circuit is operated in voltage regulation condition to drive LED for electronic sign applications. To simplify the circuit structure of the proposed hybrid converter, switches of two converters are integrated with the switch integration technique. With this approach, the proposed hybrid converter has several merits, which are less component counts, lighter weight, smaller size, and higher conversion efficiency. Finally, a prototype of LED driving system under output voltage of 10 V and output power of 20 W has been implemented to verify its feasibility. It is suitable for the electronic sign indicator applications. Sheng-Yu Tseng, Chien-Chih Chen, and Hung-Yuan Wang Copyright © 2014 Sheng-Yu Tseng et al. All rights reserved. Light-Emission and Electricity-Generation Properties of Photovoltaic Organic Light-Emitting Diodes with Rubrene/DBP Light-Emission and Electron-Donating Layers Sun, 06 Apr 2014 11:48:17 +0000 We report the dependence of the characteristics of photovoltaic organic light-emitting diodes (PVOLEDs) on the composition of the light-emission and electron-donating layer (EL-EDL). 5,6,11,12-Tetraphenylnaphthacene (rubrene): dibenzo{[f,f′]-4,4′,7,7′-tetraphenyl}diindeno[1,2,3-cd:1′,2′,3′-lm]perylene (DBP) was used to form the EL-EDL, and C60 was used as an electron-accepting layer (EAL) material. A half-gap junction was formed at the EAL/EL-EDL interface. As the rubrene ratio in the EL-EDL increased, the emission spectra became blue-shifted and the light-emission efficiency increased. The highest emission efficiency was achieved with an EL-EDL composed of 95% rubrene and 5% DBP. The short-circuit current decreased as the rubrene content increased up to 50% and then saturated, while the open-circuit voltage was almost unchanged regardless of the rubrene content. The power-conversion efficiency and fill factor increased as the composition of the EL-EDL approached that of pure materials. By controlling the rubrene : DBP ratio, the emission color could be adjusted. The emission efficiency of devices with mixed rubrene/DBP EL-EDLs could be greater than that of either pure rubrene or pure DBP devices. We obtained an overall power-conversion efficiency of 3% and a fill factor greater than 50%. Mun Soo Choi and Ho-Nyeon Lee Copyright © 2014 Mun Soo Choi and Ho-Nyeon Lee. All rights reserved. Modelling and Prediction of Photovoltaic Power Output Using Artificial Neural Networks Sun, 06 Apr 2014 11:42:33 +0000 This paper presents a solar power modelling method using artificial neural networks (ANNs). Two neural network structures, namely, general regression neural network (GRNN) feedforward back propagation (FFBP), have been used to model a photovoltaic panel output power and approximate the generated power. Both neural networks have four inputs and one output. The inputs are maximum temperature, minimum temperature, mean temperature, and irradiance; the output is the power. The data used in this paper started from January 1, 2006, until December 31, 2010. The five years of data were split into two parts: 2006–2008 and 2009-2010; the first part was used for training and the second part was used for testing the neural networks. A mathematical equation is used to estimate the generated power. At the end, both of these networks have shown good modelling performance; however, FFBP has shown a better performance comparing with GRNN. Aminmohammad Saberian, H. Hizam, M. A. M. Radzi, M. Z. A. Ab Kadir, and Maryam Mirzaei Copyright © 2014 Aminmohammad Saberian et al. All rights reserved. Photobiomodulation on KATP Channels of Kir6.2-Transfected HEK-293 Cells Sun, 06 Apr 2014 08:34:18 +0000 Background and Objective. ATP-sensitive potassium (KATP) channel couples cell metabolism to excitability. To explore role of KATP channels in cellular photobiomodulation, we designed experiment to study effect of low intensity 808 nm laser irradiation on the activity of membrane KATP channel. Study Design/Materials and Methods. Plasmids encoding Kir6.2 was constructed and heterologously expressed in cultured mammalian HEK-293 cells. The patch-clamp and data acquisition systems were used to record KATP channel current before and after irradiation. A laser beam of Ga-As 808 nm at 5 mW/cm2 was used in experiments. A one-way ANOVA test followed by a post hoc Student-Newman-Keuls test was used to assess the statistical differences between data groups. Results. Obvious openings of KATP channels of Kir6.2-transfected HEK-293 cells and excised patches were recorded during and after low intensity 808 nm laser irradiation. Compared with the channels that did not undergo irradiation, open probability, current amplitude, and dwell time of KATP channels after irradiation improved. Conclusions. Low intensity 808 nm laser irradiation may activate membrane KATP channels of Kir6.2-transfected HEK-293 cells and in excised patches. Fu-qing Zhong, Yang Li, and Xian-qiang Mi Copyright © 2014 Fu-qing Zhong et al. All rights reserved. Hierarchical Structures from Inorganic Nanocrystal Self-Assembly for Photoenergy Utilization Thu, 03 Apr 2014 11:49:23 +0000 Self-assembly has emerged as a powerful strategy for controlling the structure and physicochemical properties of ensembles of inorganic nanocrystals. Hierarchical structures from nanocrystal assembly show collective properties that differ from individual nanocrystals and bulk samples. Incorporation of structural hierarchy into nanostructures is of great importance as a result of enhancing mass transportation, reducing resistance to diffusion, and high surface areas for adsorption and reaction, and thus much effort has been devoted to the exploration of various novel organizing schemes through which inorganic porous structure with architectural design can be created. In this paper, the recent research progress in this field is reviewed. The general strategies for the synthesis of hierarchical structures assembled from nanobuilding blocks are elaborated. The well-defined hierarchical structures provide new opportunities for optimizing, tuning, and/or enhancing the properties and performance of these materials and have found applications in photoenergy utilization including photodegradation, photocatalytic H2 production, photocatalytic CO2 conversion, and sensitized solar cells, and these are discussed illustratively. Yun-Pei Zhu, Tie-Zhen Ren, Tian-Yi Ma, and Zhong-Yong Yuan Copyright © 2014 Yun-Pei Zhu et al. All rights reserved. Antimicrobial Activity of TiO2 Nanoparticle-Coated Film for Potential Food Packaging Applications Wed, 02 Apr 2014 14:12:45 +0000 Recent uses of titanium dioxide (TiO2) have involved various applications which include the food industry. This study aims to develop TiO2 nanoparticle-coated film for potential food packaging applications due to the photocatalytic antimicrobial property of TiO2. The TiO2 nanoparticles with varying concentrations (0–0.11 g/ 100 mL organic solvent) were coated on food packaging film, particularly low density polyethylene (LDPE) film. The antimicrobial activity of the films was investigated by their capability to inactivate Escherichia coli (E. coli) in an actual food packaging application test under various conditions, including types of light (fluorescent and ultraviolet (UV)) and the length of time the film was exposed to light (one–three days). The antimicrobial activity of the TiO2 nanoparticle-coated films exposed under both types of lighting was found to increase with an increase in the TiO2 nanoparticle concentration and the light exposure time. It was also found that the antimicrobial activity of the films exposed under UV light was higher than that under fluorescent light. The developed film has the potential to be used as a food packaging film that can extend the shelf life, maintain the quality, and assure the safety of food. Siti Hajar Othman, Nurul Raudhah Abd Salam, Norhazlizam Zainal, Roseliza Kadir Basha, and Rosnita A. Talib Copyright © 2014 Siti Hajar Othman et al. All rights reserved. Optical Scattering Properties of Intralipid Phantom in Presence of Encapsulated Microbubbles Wed, 02 Apr 2014 10:08:20 +0000 In imaging, contrast agents are utilized to enhance sensitivity and specificity of diagnostic modalities. In ultrasound imaging, microbubbles (MBs)—a gas-core shell-encapsulated agent—are used clinically as contrast agents. The working hypothesis of this study is that microbubbles can be employed as an intravascular contrast agent in optical imaging systems. In this work, the interaction of light and microbubbles in a turbid medium (intralipid) was investigated, particularly, the effect of MBs on the reduced scattering and absorption coefficients. Diffuse reflectance (DR) and total transmittance (TT) measurements of highly scattering intralipid suspension (0.5–5%) were measured using spectroscopic integrating sphere system in the absence and presence of Definity microbubbles. The optical properties were computed using the inverse adding doubling (IAD) software. The presence of microbubbles increased DR and decreased TT of intralipid phantoms. In the presence of MBs (0.5% volume concentration), the reflectance of the intralipid phantom increased from 35% to 100%. The reduced scattering coefficient increased significantly (30%) indicating potential use of MBs as optical contrast agents in light based modalities. Homa Assadi, Raffi Karshafian, and Alexandre Douplik Copyright © 2014 Homa Assadi et al. All rights reserved. Effects of UV-Vis Irradiation on Vanadium Etioporphyrins Extracted from Crude Oil and the Role of Nanostructured Titania Wed, 02 Apr 2014 08:54:26 +0000 The role of UV-irradiation on oil and its derivatives is particularly important for analyzing the degradability of specific oil compounds. Also, nanostructured-TiO2 is one of the most promising photocatalysts so it is expected to be useful in their degradation. However the complexity of crude oil, as well as that of the reactions involved, is such that the effect of the presence of TiO2 under illumination is not well understood. In this paper, the influence of UV-Vis irradiation on vanadium etioporphyrins, extracted from crude oil from Dos Bocas, Tabasco, Mexico, is studied using UV-Vis spectrophotometry in the absence and presence of nanostructured TiO2 or nitrogen-doped TiO2 modified with copper (N-TiO2/Cu). It is shown that the addition of water shortens the time to start photodegradation. However, once this process has initiated, the system enters a second stage, that is very similar for samples with or without water. It is also shown that the use of N-TiO2/Cu induces an important delay in the initiation of the porphyrins’ photodegradation process. Additionally, it has been found that the presence of TiO2 in samples extracted with water induces a small reduction in the photodegradation duration and, hence, that TiO2 can catalyze the degradation of petroporphyrins. Debra Jene Kirkconnell Reyes, Andrés García Saravia Ortiz de Montellano, Rudy Amilcar Trejo Tzab, Gerko Oskam, and Juan José Alvarado Gil Copyright © 2014 Debra Jene Kirkconnell Reyes et al. All rights reserved. Photobiomodulation for Cobalt Chloride-Induced Hypoxic Damage of RF/6A Cells by 670 nm Light-Emitting Diode Irradiation Tue, 01 Apr 2014 13:31:23 +0000 Objective. The goal of this study was to investigate the therapeutic efficacy of 670 nm light-emitting diode (LED) irradiation on the diabetic retinopathy (DR) using hypoxic rhesus monkey choroid-retinal (RF/6A) cells as the model system. Background Data. Treatment with light in the spectrum from red to near-infrared region has beneficial effect on tissue injury and 670 nm LED is currently under clinical investigation for retinoprotective therapy. Methods. Studies were conducted in the cultured cells under hypoxia treated by cobalt chloride (CoCl2). After irradiation by 670 nm LED with different power densities, cell viability, cytochrome C oxidase activity, and ATP concentration were measured. Results. The irradiation of 670 nm LED significantly improved cell viability, cytochrome C oxidase activity, and ATP concentration in the hypoxia RF/6A cells. Conclusion. 670 nm LED irradiation could recover the hypoxia damage caused by CoCl2. Photobiomodulation of 670 nm LED plays a potential role for the treatment of diabetic retinopathy. Shuang Li, Qiang-Li Wang, Xin Chen, and Xian-qiang Mi Copyright © 2014 Shuang Li et al. All rights reserved. Photocatalytic Active Coatings for Lignin Degradation in a Continuous Packed Bed Reactor Tue, 01 Apr 2014 11:22:52 +0000 The synthesis of immobilized catalyst on porous glass support material via the sol-gel route is reported. TiO2-P25-SiO2 + Pt, TiO2-P25-SiO2, TiOSO4_30.6 wt%, and ZnO + TiO2-P25-SiO2 catalysts were synthesized and a comparative study is done regarding morphology of coatings, degradation rates, reaction rates, dissolved carbon (DC), formation of peaks, and fluorescence of products formed from the photocatalytic degradation of lignin sulfonate obtained from a local paper plant. Through simultaneous reaction-extraction pathways applying dialysis filtration and highly porous polystyrene divinylbenzene adsorbent resin (HR-P) for solid phase extraction (SPE), an attempt has been made to isolate smaller molecules produced from photocatalytic degradation. Moreover relatively high lignin sulfonate (0.5 g/L) concentrations are used in the reactions. UV-Vis spectroscopy revealed a faster reduction in the concentration values for the aliphatic moiety compared to the aromatic moiety. Peaks were observed by both fluorescence spectroscopy and HPLC suggesting the production of new substances and fluorophores. Colin Awungacha Lekelefac, Johannes Hild, Peter Czermak, and Michael Herrenbauer Copyright © 2014 Colin Awungacha Lekelefac et al. All rights reserved. Application of Glass Fiber-Based N-Doped Titania under Visible-Light Exposure for Photocatalytic Degradation of Aromatic Pollutants Mon, 31 Mar 2014 13:44:31 +0000 Flexible glass fiber-supported nitrogen-doped titanium dioxide (GF-N-TiO2) photocatalysts with different N/Ti ratio were prepared using a dip-coating method followed by a low-temperature heat-treatment process. In addition, their photocatalytic activities were evaluated for the degradation of aromatic volatile organic compounds (VOCs) under visible-light irradiation. The prepared GF-N-TiO2 photocatalysts were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and UV-visible spectroscopy. A control photolysis test performed using an uncoated GF displayed no detectable degradation of the target compounds under visible-light irradiation. The outlet-to-inlet concentration ratios of the target pollutants obtained using the GF-N-TiO2 photocatalysts were lower than that obtained using the GF-TiO2 photocatalyst. The photocatalytic activity of GF-N-TiO2 photocatalyst increased as the N-to-Ti ratio increased from 0.06 to 0.08 but decreased gradually as the N-to-Ti ratio increased further to 0.12, suggesting the existence of optimal N/Ti ratios. The outlet-to-inlet concentration ratio of all the target compounds displayed an increasing trend as both air flow rate and inlet concentration increased. Overall, the GF-N-TiO2 photocatalysts could be applied effectively for the degradation of aromatic VOCs under visible-light irradiation when operation conditions are optimized. Wan-Kuen Jo, Seung-Ho Shin, and Ho-Hwan Chun Copyright © 2014 Wan-Kuen Jo et al. All rights reserved. Autoregulatory Feedback Mechanism of P38MAPK/Caspase-8 in Photodynamic Therapy-Hydrophilic/Lipophilic Tetra--(4-carboxyphenoxy) Phthalocyanine Zinc-Induced Apoptosis of Human Hepatocellular Carcinoma Bel-7402 Cells Mon, 31 Mar 2014 11:40:32 +0000 Photodynamic therapy (PDT) is a novel and promising antitumor treatment. Our previous study showed that hydrophilic/lipophilic tetra-α-(4-carboxyphenoxy) phthalocyanine zinc- (TαPcZn-) mediated PDT (TαPcZn-PDT) inhibits the proliferation of human hepatocellular carcinoma Bel-7402 cells by triggering apoptosis and arresting cell cycle. However, mechanisms of TαPcZn-PDT-induced apoptosis of Bel-7402 cells have not been fully clarified. In the present study, therefore, effect of TαPcZn-PDT on apoptosis, P38MAPK, p-P38MAPK, Caspase-8, Caspase-3, Bcl-2, Bid, Cytochrome c, and mitochondria membrane potential in Bel-7402 cells without or with P38MAPK inhibitor SB203580 or Caspase-8 inhibitor Ac-IEFD-CHO was investigated by haematoxylin and eosin (HE) staining assay, flow cytometry analysis of annexin V-FITC/propidium iodide (PI) double staining cells and 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide (JC-1), and immunoblot assay. We found that TαPcZn-PDT resulted in apoptosis induction, activation of P38MAPK, Caspase-8, Caspase-3, and Bid, downregulation of Bcl-2, release of Cytochrome c from mitochondria, and disruption of mitochondrial membrane potential in TαPcZn-PDT-treated Bel-7402 cells. In contrast, SB203580 or Ac-IEFD-CHO attenuated induction of apoptosis, activation of P38MAPK, Caspase-8, Caspase-3, and Bid, downregulation of Bcl-2, release of Cytochrome c from mitochondria, and disruption of mitochondrial membrane potential in TαPcZn-PDT-treated Bel-7402 cells. Taken together, we conclude that Caspase-3, Bcl-2, Bid, and mitochondria are involved in autoregulatory feedback of P38MAPK/Caspase-8 during TαPcZn-PDT-induced apoptosis of Bel-7402 cells. Yu Wang, Chunhui Xia, Wei Chen, Yuhang Chen, Yiyi Wang, and Tao Li Copyright © 2014 Yu Wang et al. All rights reserved. Design and Optimization of Fresnel Lens for High Concentration Photovoltaic System Sun, 30 Mar 2014 08:31:19 +0000 A practical optimization design is proposed, in which the solar direct light spectrum and multijunction cell response range are taken into account in combination, particularly for the Fresnel concentrators with a high concentration and a small aspect ratio. In addition, the change of refractive index due to temperature variation in outdoor operation conditions is also considered in the design stage. The calculation results show that this novel Fresnel lens achieves an enhancement of energy efficiency of about 10% compared with conventional Fresnel lens for a given solar spectrum, solar cell response, and corrected sunshine hours of different ambient temperature intervals. Lei Jing, Hua Liu, Yao Wang, Wenbin Xu, Hongxin Zhang, and Zhenwu Lu Copyright © 2014 Lei Jing et al. All rights reserved. Numerical Simulation of Carbon Nanotubes/GaAs Hybrid PV Devices with AMPS-1D Thu, 27 Mar 2014 08:04:18 +0000 The performance and characteristics of a hybrid heterojunction single-walled carbon nanotube and GaAs solar cell are modelled and numerically simulated using AMPS-1D device simulation tool. The device physics and performance with different junction parameters are analysed. The results suggest that the open-circuit voltage changes very slightly by changing the electron affinity, acceptor and donor density while the other electrical parameters reach an optimum value. Increasing the concentration of a discrete defect density in the absorber layer decreases the electrical parameters. The current-voltage characteristics, quantum efficiency, band gap, and thickness variation of the photovoltaic response will be quantitatively considered. Georgi Xosrovashvili and Nima E. Gorji Copyright © 2014 Georgi Xosrovashvili and Nima E. Gorji. All rights reserved.