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Sample records for lightly doped drain

  1. Method of making self-aligned lightly-doped-drain structure for MOS transistors

    DOEpatents

    Weiner, Kurt H.; Carey, Paul G.

    2001-01-01

    A process for fabricating lightly-doped-drains (LDD) for short-channel metal oxide semiconductor (MOS) transistors. The process utilizes a pulsed laser process to incorporate the dopants, thus eliminating the prior oxide deposition and etching steps. During the process, the silicon in the source/drain region is melted by the laser energy. Impurities from the gas phase diffuse into the molten silicon to appropriately dope the source/drain regions. By controlling the energy of the laser, a lightly-doped-drain can be formed in one processing step. This is accomplished by first using a single high energy laser pulse to melt the silicon to a significant depth and thus the amount of dopants incorporated into the silicon is small. Furthermore, the dopants incorporated during this step diffuse to the edge of the MOS transistor gate structure. Next, many low energy laser pulses are used to heavily dope the source/drain silicon only in a very shallow region. Because of two-dimensional heat transfer at the MOS transistor gate edge, the low energy pulses are inset from the region initially doped by the high energy pulse. By computer control of the laser energy, the single high energy laser pulse and the subsequent low energy laser pulses are carried out in a single operational step to produce a self-aligned lightly-doped-drain-structure.

  2. The Anomalous Effect of Interface Traps on Generation Current in Lightly Doped Drain nMOSFET's

    NASA Astrophysics Data System (ADS)

    Ma, Xiao-Hua; Gao, Hai-Xia; Cao, Yan-Rong; Chen, Hai-Feng; Hao, Yue

    2010-05-01

    The anomalous phenomenon of generation current IGD in the lightly doped drain (LDD) nMOSFET measured under the drain bias VD-step mode is reported. We propose an assumption of activated (A) and frozen (F) traps for the VD-step mode: The A traps contributes to IGD while the F process can make them lose the roles as generation centers. The A and F regions can form the F-A region. The comparison of the F and A regions decides the role of the F-A region. The experiments confirm the assumption.

  3. Short-channel drain current model for asymmetric heavily / lightly doped DG MOSFETs

    NASA Astrophysics Data System (ADS)

    Dutta, Pradipta; Syamal, Binit; Koley, Kalyan; Dutta, Arka; Sarkar, C. K.

    2017-08-01

    The paper presents a drain current model for double gate metal oxide semiconductor field effect transistors (DG MOSFETs) based on a new velocity saturation model that accounts for short-channel velocity saturation effect independently in the front and the back gate controlled channels under asymmetric front and back gate bias and oxide thickness. To determine the front and the back-channel velocity saturation, drain-induced barrier lowering is evaluated by effective gate voltages at the front and back gates obtained from surface potential at the threshold condition after considering symmetric and asymmetric front and back oxide thickness. The model also incorporates surface roughness scattering and ionized impurity scattering to estimate drain current for heavily / lightly doped channel for short-channel asymmetric DG MOSFET and a good agreement has been achieved with TCAD simulations, with a relative error of around 3-7%.

  4. Modeling the drain current and its equation parameters for lightly doped symmetrical double-gate MOSFETs

    NASA Astrophysics Data System (ADS)

    Bhartia, Mini; Chatterjee, Arun Kumar

    2015-04-01

    A 2D model for the potential distribution in silicon film is derived for a symmetrical double gate MOSFET in weak inversion. This 2D potential distribution model is used to analytically derive an expression for the subthreshold slope and threshold voltage. A drain current model for lightly doped symmetrical DG MOSFETs is then presented by considering weak and strong inversion regions including short channel effects, series source to drain resistance and channel length modulation parameters. These derived models are compared with the simulation results of the SILVACO (Atlas) tool for different channel lengths and silicon film thicknesses. Lastly, the effect of the fixed oxide charge on the drain current model has been studied through simulation. It is observed that the obtained analytical models of symmetrical double gate MOSFETs are in good agreement with the simulated results for a channel length to silicon film thickness ratio greater than or equal to 2.

  5. Hot-carrier degradation in deep-submicrometer nMOSFETs: lightly doped drain vs. large angle tilt implanted drain

    NASA Astrophysics Data System (ADS)

    Rafí, J. M.; Campabadal, F.

    2001-08-01

    The hot-carrier degradation of lightly doped drain (LDD) and large angle tilt implanted drain (LATID) nMOSFETs of a 0.35 μm CMOS technology is analysed and compared by means of I-V characterisation and charge pumping current measurements. LATID nMOSFETs are found to exhibit a significant improvement in terms of both, current drivability and hot-carrier immunity at maximum substrate current condition. The different factors which can be responsible for this improved hot-carrier resistance are investigated. It is shown that this must be attributed to a reduction of the maximum lateral electric field along the channel, but not to a minor generation of physical damage for a given electric field or to a reduced I-V susceptibility to a given amount of generated damage. Further to this analysis, the hot-carrier degradation comparison between LDD and LATID devices is extended to the whole range of gate-stress regimes and the effects of short electron injection (SEI) and short hole injection (SHI) phases on hot-carrier-stressed devices are analysed. Apart from a significant improved resistance to hot-carrier effects registered for LATID devices, a similar behaviour is observed for the two types of architectures. In this way, SEI phases are found to be an efficient tool for revealing part of the damage generated in stresses at low gate voltages, whereas the performance of a first SHI phase after stress at high gate bias is found to result in a significant additional degradation of the devices. This enhanced degradation is attributed to a sudden interface states build-up occurring in both, LDD and LATID devices, near the Si/spacer interface only under the first hot-hole injection condition.

  6. Investigation of the cutoff frequency of double linear halo lightly doped drain and source CNTFET

    NASA Astrophysics Data System (ADS)

    Hejazifar, Mohammad Javad; Sedigh Ziabari, Seyed Ali

    2014-08-01

    In this work we investigate the n-type single halo implantation in channel of lightly doped drain and source CNTFET (SH-LDDS-CNTFET) and propose the n-type double linear halo implantation in the channel of LDDS-CNTFET. These transistors are simulated with a non-equilibrium Green's function method. We demonstrate that in the proposed structure the f T at the V GS ranges of 0-0.25 V and more than 0.42 V is much higher compared to the LDDS-CNTFET and SH-LDDS-CNTFET and the SH-LDDS-CNTFET, respectively. Finally, simulations demonstrate that the f T of the proposed transistor is more than the LDDS-CNTFET at a wide range of V GS, whereas the f T of SH-LDDS-CNTFET is more than the LDDS-CNTFET for narrow ranges of V GS.

  7. Study of novel junctionless Ge n-Tunneling Field-Effect Transistors with lightly doped drain (LDD) region

    NASA Astrophysics Data System (ADS)

    Liu, Xiangyu; Hu, Huiyong; Wang, Bin; Wang, Meng; Han, Genquan; Cui, Shimin; Zhang, Heming

    2017-02-01

    In this paper, a novel junctionless Ge n-Tunneling Field-Effect Transistors (TFET) structure is proposed. The simulation results show that Ion = 5.5 × 10-5A/μm is achieved. The junctionless device structure enhances Ion effectively and increases the region where significant BTBT occurs, comparing with the normal Ge-nTEFT. The impact of the lightly doped drain (LDD) region is investigated. A comparison of Ion and Ioff of the junctionless Ge n-TFET with different channel doping concentration ND and LDD doping concentration NLDD is studied. Ioff is reduced 1 order of magnitude with the optimized ND and NLDD are 1 × 1018cm-3 and 1 × 1017 cm-3, respectively. To reduce the gate induced drain leakage (GIDL) current, the impact of the sloped gate oxide structure is also studied. By employing the sloped gate oxide structure, the below 60 mV/decade subthreshold swing S = 46.2 mV/decade is achieved at Ion = 4.05 × 10-5A/μm and Ion/Ioff = 5.7 × 106.

  8. A Modified Lightly Doped Drain Structure for VLSI MOSFET’s,

    DTIC Science & Technology

    1986-01-01

    channel current away from the SiO 2 interface in the high field drain region. Techniques proposed to accomplish this include either a buried channel device...measurements were done at the wafer level utilizing a floating gate induced drain current relaxation technique demonstrated in [70]. Resolution below 10-1 A...was possible with this technique . Gate current comparisons presented herein are for devices built side by side on the same chip, since small structural

  9. Hetero-junction carbon nanotube FET with lightly doped drain and source regions

    NASA Astrophysics Data System (ADS)

    Yousefi, Reza; Doorzad, Leila

    2016-01-01

    In this paper, a new structure was introduced for carbon nanotube (CNT) MOSFET transistors. The proposed structure was composed of two different nanotubes for the source/drain and channel regions. Electrical characteristics of this structure were investigated using nonequilibrium Green’s function approach. Results of the simulations demonstrated that the proposed hetero-structure had almost the same ON-current and much less OFF-current and as a result higher ION/IOFF ratio than the conventional homo-structure. Results of the comparison between switching behavior in equal ION/IOFF ratio showed that, although the proposed structure had longer delay, its power dissipation for every switching event was less than that of the conventional structure. A further comparison of the switching characteristic in equal ON-current values showed that the proposed structure enjoys from shorter delay and also consumes less power-delay product (PDP) when compared to the LDDS structure.

  10. Improved Radio Frequency Power Characteristics of Complementary Metal-Oxide-Semiconductor-Compatible Asymmetric-Lightly-Doped-Drain Metal-Oxide-Semiconductor Transistor

    NASA Astrophysics Data System (ADS)

    Chang, Tsu; Kao, Hsuan-ling; Chen, Y. J.; Chin, Albert

    2010-03-01

    We have characterized and modeled the radio frequency (RF) power performance of a 0.18 µm asymmetric-lightly-doped-drain metal-oxide-semiconductor field-effect transistor (LDD MOSFET). In comparison with the conventional 0.18 µm MOSFET, this asymmetric-LDD device shows a larger power density of 0.54 W/mm, and 8 dB better adjacent channel power ratio (ACPR) linearity at 2.4 GHz from the improved twice DC breakdown voltage of 6.9 V. These significant improvements of RF power performance in the asymmetric-LDD transistor are important for the medium RF power amplifier application.

  11. Improved Radio Frequency Power Characteristics of Complementary Metal-Oxide-Semiconductor-Compatible Asymmetric-Lightly-Doped-Drain Metal-Oxide-Semiconductor Transistor

    NASA Astrophysics Data System (ADS)

    Tsu Chang,; Hsuan-ling Kao,; Y. J. Chen,; Albert Chin,

    2010-03-01

    We have characterized and modeled the radio frequency (RF) power performance of a 0.18 μm asymmetric-lightly-doped-drain metal-oxide-semiconductor field-effect transistor (LDD MOSFET). In comparison with the conventional 0.18 μm MOSFET, this asymmetric-LDD device shows a larger power density of 0.54 W/mm, and 8 dB better adjacent channel power ratio (ACPR) linearity at 2.4 GHz from the improved twice DC breakdown voltage of 6.9 V. These significant improvements of RF power performance in the asymmetric-LDD transistor are important for the medium RF power amplifier application.

  12. LIGHT regulates inflamed draining lymph node hypertrophy

    PubMed Central

    Zhu, Mingzhao; Yang, Yajun; Wang, Yugang; Wang, Zhongnan; Fu, Yang-Xin

    2011-01-01

    Lymph node (LN) hypertrophy, the increased cellularity of LNs, is the major indication of the initiation and expansion of the immune response against infection, vaccination, cancer or autoimmunity. The mechanisms underlying LN hypertrophy remain poorly defined. Here, we demonstrate that LIGHT (TNFSF14) is a novel factor essential for LN hypertrophy after CFA immunization. Mechanistically, LIGHT is required for the influx of lymphocytes into but not egress out of LNs. In addition, LIGHT is required for DC migration from the skin to draining LNs. Compared with WT mice, LIGHT−/− mice express lower levels of chemokines in skin and addressins in LN vascular endothelial cells after CFA immunization. We unexpectedly observed that LIGHT from radioresistant rather than radiosensitive cells, likely Langerhans cells, is required for LN hypertrophy. Importantly, antigen-specific T cell responses were impaired in DLN of LIGHT−/− mice, suggesting the importance of LIGHT regulation of LN hypertrophy in the generation of an adaptive immune response. Collectively, our data reveal a novel cellular and molecular mechanism for the regulation of LN hypertrophy and its potential impact on the generation of an optimal adaptive immune response. PMID:21572030

  13. SLD-MOSCNT: A new MOSCNT with step-linear doping profile in the source and drain regions

    NASA Astrophysics Data System (ADS)

    Tahne, Behrooz Abdi; Naderi, Ali

    2017-01-01

    In this paper, a new structure, step-linear doping MOSCNT (SLD-MOSCNT), is proposed to improve the performance of basic MOSCNTs. The basic structure suffers from band to band tunneling (BTBT). We show that using SLD profile for source and drain regions increases the horizontal distance between valence and conduction bands at gate to source/drain junction which reduces BTBT probability. SLD performance is compared with other similar structures which have recently been proposed to reduce BTBT such as MOSCNT with lightly-doped drain and source (LDDS), and with double-light doping in source and drain regions (DLD). The obtained results using a nonequilibrium Green’s function (NEGF) method show that the SLD-MOSCNT has the lowest leakage current, power consumption and delay time, and the highest current ratio and voltage gain. The ambipolar conduction in the proposed structure is very low and can be neglected. In addition, these structures can improve short-channel effects. Also, the investigation of cutoff frequency of the different structures shows that the SLD has the highest cutoff frequency. Device performance has been investigated for gate length from 8 to 20 nm which demonstrates all discussions regarding the superiority of the proposed structure are also valid for different channel lengths. This improvement is more significant especially for channel length less than 12 nm. Therefore, the SLD can be considered as a candidate to be used in the applications with high speed and low power consumption.

  14. Effects of drain doping concentration on switching characteristics of tunnel field-effect transistor inverters

    NASA Astrophysics Data System (ADS)

    Kwon, Dae Woong; Kim, Jang Hyun; Park, Byung-Gook

    2016-11-01

    In order to investigate the effects of the modulation of drain doping concentration (N drain) on alternating current (AC) switching characteristics of a tunnel filed-effect transistor (TFET) inverter, the characteristics of TFETs with various N drains are analyzed rigorously through mixed-mode device and circuit TCAD simulations. As the N drain gets decreased, the drain current (I D) becomes reduced and the gate-to-drain capacitance (C GD) reflects the entire gate capacitance (C GG) at a lower gate voltage (V G), which leads to the degradation of falling/rising delay in TFET inverters. These phenomena are explained successfully by the change of quasi-Fermi energy in the drain (E F_drain) as a function of V G. The E F_drain rises dramatically from when tunneling current starts to flow from the source in the n-type TFET with low N drain. As a result, drain-side channel inversion occurs at a lower V G due to the reduction of the energy barrier between the E F_drain and the conduction band edge of the channel.

  15. Incubational domain characterization in lightly doped ceria

    SciTech Connect

    Li Zhipeng; Mori, Toshiyuki; John Auchterlonie, Graeme; Zou Jin; Drennan, John

    2012-08-15

    Microstructures of both Gd- and Y-doped ceria with different doping level (i.e., 10 at% and 25 at%) have been comprehensively characterized by means of high resolution transmission electron microscopy and selected area electron diffraction. Coherent nano-sized domains can be widely observed in heavily doped ceria. Nevertheless, it was found that a large amount of dislocations actually exist in lightly doped ceria instead of heavily doped ones. Furthermore, incubational domains can be detected in lightly doped ceria, with dislocations located at the interfaces. The interactions between such linear dislocations and dopant defects have been simulated accordingly. As a consequence, the formation mechanism of incubational domains is rationalized in terms of the interaction between intrinsic dislocations of doped ceria and dopant defects. This study offers the insights into the initial state and related mechanism of the formation of nano-sized domains, which have been widely observed in heavily rare-earth-doped ceria in recent years. - Graphical abstract: Interactions between dislocations and dopants lead to incubational domain formation in lightly doped ceria. Highlights: Black-Right-Pointing-Pointer Microstructures were characterized in both heavily and light Gd-/Y-doped ceria. Black-Right-Pointing-Pointer Dislocations are existed in lightly doped ceria rather than heavily doped one. Black-Right-Pointing-Pointer Interactions between dislocations and dopant defects were simulated. Black-Right-Pointing-Pointer Formation of dislocation associated incubational domain is rationalized.

  16. Effects of Body Doping in a NAND Flash String without Source/Drain

    NASA Astrophysics Data System (ADS)

    Kim, Young Min; Cho, Il Hwan; Kwon, Hyuck-In; Lee, Jong-Ho

    2011-11-01

    Cell structure using fringing field from control gate (CG) is very promising for a scaled NAND flash memory beyond sub-40 nm node. We investigated a new NAND string structure not with n-type source/drain (S/D) regions but with p-type regions in the space between gates. Even though the NAND string has a p-type region instead of n-type S/D in the space between adjacent two cells, induced layer (virtual source/drain) can be easily formed in the space by the fringing field from the CGs. When comparing a conventional NAND string with n-type S/D, the proposed structure shows better drain induced barrier leakage (DIBL) and subthreshold swing (SS) characteristics, and also shows better immunity against the process variation than conventional structure with n-type S/D. The electrical characteristics of the proposed structure were investigated as parameters of the width and doping concentration at the p/n-type region. As a NAND cell string, the current drivability of the proposed structure was also studied.

  17. A new analytical drain current model of cylindrical gate silicon tunnel FET with source δ-doping

    NASA Astrophysics Data System (ADS)

    Dash, Sidhartha; Jena, Biswajit; Mishra, Guru Prasad

    2016-09-01

    A new δ-doped cylindrical gate silicon tunnel FET (DCG-TFET) analytical model is developed and investigated extensively, with the aim of addressing the challenges of the conventional CG-TFET. The improvement in tunneling probability of charge carriers has been achieved by inserting a δ-doping sheet in the source region which leads to high drain current as compared to CG-TFET. The effect of distance between the δ-doping sheet and source/channel interface on the current performance, sub-threshold swing (SS) and threshold voltage (Vth) has been examined. The instantaneous position of δ-doping region from the tunneling junction is optimized based on the trade-off between current ratio and SS. The present model exhibit maximum switching current ratio (ION/IOFF ≅1012) for an optimum distance of 2 nm without degrading SS (SS∼55 mV/decade) and Vth performance. The electrostatic behavior of the present model is obtained using the solution of Poisson's equation in the cylindrical coordinate system. However the impact of scaling of the gate oxide thickness and cylindrical pillar diameter on drain current performance has been discussed. In future, DCG-TFET can be one of the potential successors for ultra-low-power applications because of its improved drain current and switching ratio.

  18. Subthreshold Current and Swing Modeling of Gate Underlap DG MOSFETs with a Source/Drain Lateral Gaussian Doping Profile

    NASA Astrophysics Data System (ADS)

    Singh, Kunal; Kumar, Sanjay; Goel, Ekta; Singh, Balraj; Kumar, Mirgender; Dubey, Sarvesh; Jit, Satyabrata

    2017-01-01

    This paper proposes a new model for the subthreshold current and swing of the short-channel symmetric underlap ultrathin double gate metal oxide field effect transistors with a source/drain lateral Gaussian doping profile. The channel potential model already reported earlier has been utilized to formulate the closed form expression for the subthreshold current and swing of the device. The effects of the lateral straggle and geometrical parameters such as the channel length, channel thickness, and oxide thickness on the off current and subthreshold slope have been demonstrated. The devices with source/drain lateral Gaussian doping profiles in the underlap structure are observed to be highly resistant to short channel effects while improving the current drive. The proposed model is validated by comparing the results with the numerical simulation data obtained by using the commercially available ATLAS™, a two-dimensional (2-D) device simulator from SILVACO.

  19. Investigating the impact of source/drain doping dependent effective masses on the transport characteristics of ballistic Si-nanowire field-effect-transistors

    SciTech Connect

    Nag Chowdhury, Basudev; Chattopadhyay, Sanatan

    2014-03-28

    This article studies the impact of doping dependent carrier effective masses of the source/drain regions on transport properties of Si-nanowire field effect transistors within ballistic limit. The difference of carrier effective mass in channel and that in the source/drain regions leads to a misalignment of respective sub-bands and forms non-ideal contacts. Such non-idealities are incorporated by modifying the relevant self-energies which control the effective electronic transport from source to drain through the channel. Non-ideality also arises in the nature of local density of states in the channel due to sub-band misalignment, resulting to a reduction of drain current by almost 50%. The highest values of drain current, leakage current, and their ratio are obtained for the S/D doping concentrations of 3 × 10{sup 20} cm{sup −3}, 8 × 10{sup 20} cm{sup −3}, and 2 × 10{sup 20} cm{sup −3}, respectively, for the nanowire of length 10 nm and diameter of 3 nm. Interestingly, the maximum of sub-threshold swing, minimum of threshold voltage, and the maximum of leakage current are observed to be apparent at the same doping concentration.

  20. Bottom-gate poly-Si thin-film transistors by nickel silicide seed-induced lateral crystallization with self-aligned lightly doped layer

    NASA Astrophysics Data System (ADS)

    Lee, Sol Kyu; Seok, Ki Hwan; Chae, Hee Jae; Lee, Yong Hee; Han, Ji Su; Jo, Hyeon Ah; Joo, Seung Ki

    2017-03-01

    We report a novel method to reduce source and drain (S/D) resistances, and to form a lightly doped layer (LDL) of bottom-gate polycrystalline silicon (poly-Si) thin-film transistors (TFTs). For application in driving TFTs, which operate under high drain voltage condition, poly-Si TFTs are needed in order to attain reliability against hot-carriers as well as high field-effect mobility (μFE). With an additional doping on the p+ Si layer, sheet resistance on S/D was reduced by 37.5% and an LDL was introduced between the channel and drain. These results contributed to not only a lower leakage current and gate-induced drain leakage, but also high immunity of kink-effect and hot-carrier stress. Furthermore, the measured electrical characteristics exhibited a steep subthreshold slope of 190 mV/dec and high μFE of 263 cm2/Vs.

  1. Design and simulation of double-lightly doped MOSCNT using non-equilibrium Green's function

    NASA Astrophysics Data System (ADS)

    Moghadam, Narjes; Aziziyan, Mohammad Reza; Fathi, Davood

    2012-09-01

    In this paper, we propose a new ohmic-structure of ballistic carbon nanotube field-effect transistors (CNTFETs) in which the source and drain regions are doped stepwise and the device acts as MOSFET like CNTFET (MOSCNT). The number of lightly doped regions and their doping concentrations are optimized to obtain the lowest OFF current. To study the device characteristics, the Poisson-Schrödinger equations are solved self-consistently using the Nonequilibrium Green's Function (NEGF) formalism in the mode space approach. To find the Hamiltonian matrix, the tight-binding approximation with only p z orbital is used. The obtained results show that the stepwise regions lead to barrier widening due to the reduction in potential gradient. Therefore, the band-to-band tunneling (BTBT) and the ambipolar behavior of the device decrease due to band engineering. This causes to the superior reduction of OFF current and dissipative power. In addition, the device performance shows lower subthreshold swing (SS), smaller drain induced barrier lowering (DIBL), and larger current ratio than that of the previous structures.

  2. Co doped ZnO nanowires as visible light photocatalysts

    NASA Astrophysics Data System (ADS)

    Šutka, Andris; Käämbre, Tanel; Pärna, Rainer; Juhnevica, Inna; Maiorov, Mihael; Joost, Urmas; Kisand, Vambola

    2016-06-01

    High aspect ratio cobalt doped ZnO nanowires showing strong photocatalytic activity and moderate ferromagnetic behaviour were successfully synthesized using a solvothermal method and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), vibrating sample magnetometry (VSM) and UV-visible absorption spectroscopy. The photocatalytic activities evaluated for visible light driven degradation of an aqueous methylene orange (MO) solution were higher than for Co doped ZnO nanoparticles at the same doping level and synthesized by the same synthesis route. The rate constant for MO visible light photocatalytic degradation was 1.9·10-3 min-1 in case of nanoparticles and 4.2·10-3 min-1 in case of nanowires. We observe strongly enhanced visible light photocatalytic activity for moderate Co doping levels, with an optimum at a composition of Zn0.95Co0.05O. The enhanced photocatalytic activities of Co doped ZnO nanowires were attributed to the combined effects of enhanced visible light absorption at the Co sites in ZnO nanowires, and improved separation efficiency of photogenerated charge carriers at optimal Co doping.

  3. Impactful study of dual work function, underlap and hetero gate dielectric on TFET with different drain doping profile for high frequency performance estimation and optimization

    NASA Astrophysics Data System (ADS)

    Yadav, Dharmendra Singh; Sharma, Dheeraj; Raad, Bhagwan Ram; Bajaj, Varun

    2016-08-01

    This manuscript presents a comparative study of different combination for the dual workfunction gate material, underlap and hetero gate dielectric tunnel field-effect transistors (TFET's). Their performances have been analyzed in terms of ON-state current, ambipolar behaviour and RF response along with different drain doping profile. For this, the Dual work function of gate provides enhancement in ON-state current by reducing the tunnel barrier width at source/channel interface. Whereas, the underlap of gate is done near to the drain region, helps in reduction of ambipolar conduction by creating deficiency of hole for the conduction, which is major hurdle for TFET. Further, the combinations of the dual workfunction and underlap give combine advantages of both such as improve ON-state current and suppressed ambipolar current. Apart from this, the combination of hetero gate dielectric dual workfunction under lapping leads to superior device performance in terms of ON-state current and ambipolar behaviour. The use of hetero gate dielectric and Gaussian doping profile with gate underlap reduces the gate to drain capacitance that also improves the RF parameters of the device.

  4. Single-poly EEPROM cell with lightly doped MOS capacitors

    DOEpatents

    Riekels, James E.; Lucking, Thomas B.; Larsen, Bradley J.; Gardner, Gary R.

    2008-05-27

    An Electrically Erasable Programmable Read Only Memory (EEPROM) memory cell and a method of operation are disclosed for creating an EEPROM memory cell in a standard CMOS process. A single polysilicon layer is used in combination with lightly doped MOS capacitors. The lightly doped capacitors employed in the EEPROM memory cell can be asymmetrical in design. Asymmetrical capacitors reduce area. Further capacitance variation caused by inversion can also be reduced by using multiple control capacitors. In addition, the use of multiple tunneling capacitors provides the benefit of customized tunneling paths.

  5. Light Scattering in Nanoparticle Doped Transparent Polyimide Substrates.

    PubMed

    Shen, Jiulin; Li, Fu; Cao, Zhonghuan; Barat, David; Tu, Guoli

    2017-05-03

    Here we demonstrate a simple and effective method of fabricating polymeric scattering substrate for flexible organic light-emitting diodes (OLEDs) that require no costly patterning, etching, or molding processes, aspects that are desirable for the commercialization of large-scale lighting panels. Systematic study of the influences of relative index of refraction, particle size, and doping concentration on transmittance and haze of transparent colorless polyimide (cPI) films was carried out. It was found that the reduction of transmittance and haze of the doped films decreases along with the decrease of the difference of refractive index between the particles and polymer matrix, and it could be compensated by the increase of particle size or doping concentration.

  6. Slow light propagation in a ring erbium-doped fiber.

    PubMed

    Bencheikh, K; Baldit, E; Briaudeau, S; Monnier, P; Levenson, J A; Mélin, G

    2010-12-06

    Slow light propagation is demonstrated by implementing Coherent Population Oscillations in a silica fiber doped with erbium ions in a ring surrounding the single mode core. Though only the wings of the mode interact with erbium ions, group velocities around 1360 m/s are obtained without any spatial distortion of the propagating mode.

  7. Origin of electrophosphorescence from a doped polymer light emitting diode

    NASA Astrophysics Data System (ADS)

    Lane, P. A.; Palilis, L. C.; O'brien, D. F.; Giebeler, C.; Cadby, A. J.; Lidzey, D. G.; Campbell, A. J.; Blau, W.; Bradley, D. D.

    2001-06-01

    The origin of electrophosphorescence from a doped polymer light emitting diode (LED) has been investigated. A luminescent polymer host, poly(9,9-dioctylfluorene) (PFO), was doped with a red phosphorescent dye, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (PtOEP). The maximum external quantum efficiency of 3.5% was obtained at a concentration of 4% PtOEP by weight. Energy transfer mechanisms between PFO and PtOEP were studied by absorption, photoluminescence, and photoinduced absorption spectroscopy. Even though electroluminescence spectra were dominated by PtOEP at a concentration of only 0.2 wt % PtOEP, Förster transfer of singlet excitons was weak and there was no evidence for Dexter transfer of triplet excitons. We conclude that the dominant emission mechanism in doped LED's is charge trapping followed by recombination on PtOEP molecules.

  8. Origin of electrophosphorescence from a doped polymer light emitting diode

    SciTech Connect

    Lane, P. A.; Palilis, L. C.; O {close_quote}Brien, D. F.; Giebeler, C.; Cadby, A. J.; Lidzey, D. G.; Campbell, A. J.; Blau, W.; Bradley, D. D. C.

    2001-06-15

    The origin of electrophosphorescence from a doped polymer light emitting diode (LED) has been investigated. A luminescent polymer host, poly(9,9-dioctylfluorene) (PFO), was doped with a red phosphorescent dye, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (PtOEP). The maximum external quantum efficiency of 3.5% was obtained at a concentration of 4% PtOEP by weight. Energy transfer mechanisms between PFO and PtOEP were studied by absorption, photoluminescence, and photoinduced absorption spectroscopy. Even though electroluminescence spectra were dominated by PtOEP at a concentration of only 0.2 wt% PtOEP, Forster transfer of singlet excitons was weak and there was no evidence for Dexter transfer of triplet excitons. We conclude that the dominant emission mechanism in doped LED{close_quote}s is charge trapping followed by recombination on PtOEP molecules.

  9. Work Function Tuning and Doping Optimization of 22-nm HKMG Raised SiGe/SiC Source-Drain FinFETs

    NASA Astrophysics Data System (ADS)

    Rezali, F. A. Md; Rasid, M. A. S. Abd; Othman, N. A. F.; Hatta, S. Wan Muhamad; Soin, N.

    2017-01-01

    The basic requirements on process design of extremely scaled devices involve appropriate work function and tight doping control due to their significant effect on the threshold voltage as well as other critical electrical parameters such as drive current and leakage. This paper presents a simulation study of 22-nm fin field-effect transistor (FinFET) performance based on various process design considerations including metal gate work function (WF), halo doping (N halo), source/drain doping (N sd), and substrate doping (N sub). The simulations suggest that the n-type FinFET (nFinFET) operates effectively with lower metal gate WF while the p-type FinFET (pFinFET) operates effectively with high metal gate WF in 22-nm strained technology. Further investigation shows that the leakage reduces with increasing N halo, decreasing N sd, and increasing N sub. Taguchi and Pareto analysis-of-variance approaches are applied using an L27 orthogonal array combined with signal-to-noise ratio analysis to determine the best doping concentration combination for 22-nm FinFETs in terms of threshold voltage (V t), saturation current (I on), and off-state current (I off). Since there is a tradeoff between I on and I off, the design with the nominal-is-best V t characteristic is proposed, achieving nominal V t of 0.259 V for the nFinFET and -0.528 V for the pFinFET. Pareto analysis revealed N halo and N sub to be the dominant factor for nFinFET and pFinFET performance, respectively.

  10. Work Function Tuning and Doping Optimization of 22-nm HKMG Raised SiGe/SiC Source-Drain FinFETs

    NASA Astrophysics Data System (ADS)

    Rezali, F. A. Md; Rasid, M. A. S. Abd; Othman, N. A. F.; Hatta, S. Wan Muhamad; Soin, N.

    2017-03-01

    The basic requirements on process design of extremely scaled devices involve appropriate work function and tight doping control due to their significant effect on the threshold voltage as well as other critical electrical parameters such as drive current and leakage. This paper presents a simulation study of 22-nm fin field-effect transistor (FinFET) performance based on various process design considerations including metal gate work function (WF), halo doping ( N halo), source/drain doping ( N sd), and substrate doping ( N sub). The simulations suggest that the n-type FinFET ( nFinFET) operates effectively with lower metal gate WF while the p-type FinFET ( pFinFET) operates effectively with high metal gate WF in 22-nm strained technology. Further investigation shows that the leakage reduces with increasing N halo, decreasing N sd, and increasing N sub. Taguchi and Pareto analysis-of-variance approaches are applied using an L27 orthogonal array combined with signal-to-noise ratio analysis to determine the best doping concentration combination for 22-nm FinFETs in terms of threshold voltage ( V t), saturation current ( I on), and off-state current ( I off). Since there is a tradeoff between I on and I off, the design with the nominal-is-best V t characteristic is proposed, achieving nominal V t of 0.259 V for the nFinFET and -0.528 V for the pFinFET. Pareto analysis revealed N halo and N sub to be the dominant factor for nFinFET and pFinFET performance, respectively.

  11. Emission Characteristics and Effect of Battery Drain in "Budget" Curing Lights.

    PubMed

    AlShaafi, M M; Harlow, J E; Price, H L; Rueggeberg, F A; Labrie, D; AlQahtani, M Q; Price, R B

    2016-01-01

    Recently, "budget" dental light-emitting diode (LED)-based light-curing units (LCUs) have become available over the Internet. These LCUs claim equal features and performance compared to LCUs from major manufacturers, but at a lower cost. This study examined radiant power, spectral emission, beam irradiance profiles, effective emission ratios, and the ability of LCUs to provide sustained output values during the lifetime of a single, fully charged battery. Three examples of each budget LCU were purchased over the Internet (KY-L029A and KY-L036A, Foshan Keyuan Medical Equipment Co, and the Woodpecker LED.B, Guilin Woodpecker Medical Instrument Co). Major dental manufacturers provided three models: Elipar S10 and Paradigm (3M ESPE) and the Bluephase G2 (Ivoclar Vivadent). Radiant power emissions were measured using a laboratory-grade thermopile system, and the spectral emission was captured using a spectroradiometer system. Irradiance profiles at the tip end were measured using a modified laser beam profiler, and the proportion of optical tip area that delivered in excess of 400 mW/cm(2) (termed the effective emission ratio) was displayed using calibrated beam profile images. Emitted power was monitored over sequential exposures from each LCU starting at a fully charged battery state. The results indicated that there was less than a 100-mW/cm(2) difference between manufacturer-stated average tip end irradiance and the measured output. All the budget lights had smaller optical tip areas, and two demonstrated lower effective emission ratios than did the units from the major manufacturers. The budget lights showed discontinuous values of irradiance over their tip ends. One unit delivered extremely high output levels near the center of the light tip. Two of the budget lights were unable to maintain sustained and stable light output as the battery charge decreased with use, whereas those lights from the major manufacturers all provided a sustained light output for at least

  12. Thermal evolution of exchange interactions in lightly doped barium hexaferrites

    NASA Astrophysics Data System (ADS)

    Trukhanov, S. V.; Trukhanov, A. V.; Kostishyn, V. G.; Panina, L. V.; Turchenko, V. A.; Kazakevich, I. S.; Trukhanov, An. V.; Trukhanova, E. L.; Natarov, V. O.; Balagurov, A. M.

    2017-03-01

    The lightly doped BaFe12-xDxO19 (D=Al3+, In3+; x=0.1 and 0.3) polycrystalline hexaferrite samples have been investigated by powder neutron diffractometry as well as by vibration sample magnetometry in a wide temperature range from 4 K up to 740 K and in magnetic field up to 14 T to establish the nature of Fe3+(Al3+, In3+) - O2- - Fe3+(Al3+, In3+) indirect exchange interactions. The crystal structure features such as the ionic coordinates and lattice parameters have been defined and Rietveld refined. The Invar effect has been observed in low temperature range below 150 K. It was explained by the thermal oscillation anharmonicity of ions. It is established that the ferrimagnet-paramagnet phase transition is a standard second-order one. From the macroscopic magnetization measurement the Curie temperature and ordered magnetic moment per nominal iron ion are obtained. From the microscopic diffraction measurement the magnetic moments at all the nonequivalent ionic positions and total magnetic moment per iron ion have been obtained at different temperatures down to 4 K. The light diamagnetic doping mechanism and magnetic structure model are proposed. The effect of light diamagnetic doping on nature of Fe3+(Al3+, In3+) - O2- - Fe3+(Al3+, In3+) indirect exchange interactions with temperature increase is discussed.

  13. Characteristics of n-Type Asymmetric Schottky-Barrier Transistors with Silicided Schottky-Barrier Source and Heavily n-Type Doped Channel and Drain

    NASA Astrophysics Data System (ADS)

    Lin, Zer-Ming; Lin, Horng-Chih; Huang, Tiao-Yuan

    2012-06-01

    In this study, we explore the operation of operation a novel asymmetric Schottky-barrier transistor (ASSBT) through using technology computer aided design (TCAD). The new ASSBT features a silicided Schottky-barrier (SB) source, with the channel and drain made of heavily n-doped silicon. By eliminating the SB drain junction contained in conventional symmetrical-type SB metal-oxide-semiconductor field-effect transistors (MOSFETs), a larger on-state current is achievable. Moreover, combined with the adoption of fully depleted thin-film channel, the off-state leakage current can be efficiently suppressed as well. In addition, we also comprehensively analyze the transport mechanisms dominating in different operational regions of this new ASSBT. A pseudo-subthreshold region that shows worse subthreshold swing (SS) than the subthreshold region is identified. A decrease in channel and/or gate oxide thicknesses can contribute to the improvement of the SS of this region. A modified form of scaling length (λ) is also introduced to describe the impacts of structural parameters and gate configurations on the SS characteristics of this new ASSBT.

  14. White light generation from Dy3+ doped tellurite glass

    NASA Astrophysics Data System (ADS)

    Damak, Kamel; Yousef, El Sayed; Rüssel, Christian; Maâlej, Ramzi

    2014-02-01

    This paper reports on the spectral results of Dy3+ (1.0 mol%) ions-doped TeO2-ZnO-PbO-PbF2-Na2O (TZPPN) glass. Raman spectrum measurements, differential thermal analysis (DTA) profiles of this rare-earth ion-doped glass were carried out. From the DTA thermogram, glass transition (Tg), crystallization (Tc) and melting (Tm) temperatures were evaluated. Direct and indirect optical band gaps were calculated based on the glasses UV absorption spectra. From the absorption spectra, Judd-Ofelt (J-O) intensity parameters, Ωk, were calculated. Using J-O intensity parameters, several radiative properties such as spontaneous transition probabilities (AR), radiative branching ratios (βR) and radiative lifetimes (τR) were determined for the excitation level 4F9/2. From the emission spectra, a strong yellow emission at 574 nm (4F9/2→6H13/2) was observed and it also showed a combination of blue and red emission bands for this glass. The stimulated emission cross-section σ(λp) was also evaluated for the 4F9/2→6HJ (J=11/2, 13/2, and 15/2) transitions. This study indicates that 1 mol% Dy2O3-doped tellurite glass can be considered for white light generation with the excitation of blue light (454 nm).

  15. P-doping-free III-nitride high electron mobility light-emitting diodes and transistors

    SciTech Connect

    Li, Baikui; Tang, Xi; Chen, Kevin J.; Wang, Jiannong

    2014-07-21

    We report that a simple metal-AlGaN/GaN Schottky diode is capable of producing GaN band-edge ultraviolet emission at 3.4 eV at a small forward bias larger than ∼2 V at room temperature. Based on the surface states distribution of AlGaN, a mature impact-ionization-induced Fermi-level de-pinning model is proposed to explain the underlying mechanism of the electroluminescence (EL) process. By experimenting with different Schottky metals, Ni/Au and Pt/Au, we demonstrated that this EL phenomenon is a “universal” property of metal-AlGaN/GaN Schottky diodes. Since this light-emitting Schottky diode shares the same active structure and fabrication processes as the AlGaN/GaN high electron mobility transistors, straight-forward and seamless integration of photonic and electronic functional devices has been demonstrated on doping-free III-nitride heterostructures. Using a semitransparent Schottky drain electrode, an AlGaN/GaN high electron mobility light-emitting transistor is demonstrated.

  16. Salt-Doped Polymer Light-Emitting Devices

    NASA Astrophysics Data System (ADS)

    Gautier, Bathilde

    Polymer Light-Emitting Electrochemical Cells (PLECs) are solid state devices based on the in situ electrochemical doping of the luminescent polymer and the formation of a p-n junction where light is emitted upon the application of a bias current or voltage. PLECs answer the drawbacks of polymer light-emitting diodes as they do not require an ultra-thin active layer nor are they reliant on low work function cathode materials that are air unstable. However, because of the dynamic nature of the doping, they suffer from slow response times and poor stability over time. Frozen-junction PLECs offer a solution to these drawbacks, yet they are impractical due to their sub-ambient operation temperature requirement. Our work presented henceforth aims to achieve room temperature frozen-junction PLECS. In order to do that we removed the ion solvating/transporting polymer from the active layer, resulting in a luminescent polymer combined solely with a salt sandwiched between an ITO electrode and an aluminum electrode. The resulting device was not expected to operate like a PLEC due to the absence of an ion-solvating and ion-transporting medium. However, we discovered that the polymer/salt devices could be activated by applying a large voltage bias, resulting in much higher current and luminance. More important, the activated state is quasi static. Devices based on the well-known orange-emitting polymer MEH-PPV displayed a luminance storage half-life of 150 hours when activated by forward bias (ITO biased positively with respect to the aluminum) and 200 hours when activated by reverse bias. More remarkable yet, devices based on a green co-polymer displayed no notable decay in current density or luminance even after being stored for 1200 hours at room temperature! PL imaging under UV excitation demonstrates the presence of doping. These devices are described herein along with an explanation of their operating mechanisms.

  17. Strongly enhanced thermal transport in a lightly doped Mott insulator

    NASA Astrophysics Data System (ADS)

    Zlatic, Veljko; Freericks, Jim

    2013-03-01

    We discuss the charge and heat transport of a ``bad metal'' described by the Falicov-Kimball model near half-filling, using DMFT. For a lightly doped Mott insulator, the exact solution gives transport coefficients of a universal form at low, T <=T0 , and high temperatures, T >=Tμ . These characteristic temperatures are such that, for T <=T0 , transport is not affected by the excitations across the gap and that, for T >=Tμ , the chemical potential is at the center of the gap. At intermediate temperatures, T0 <= T <=Tμ , the chemical potential moves in the gap and the Wiedemann-Franz law doesn't hold. Here, the increased asymmetry of the electron and hole currents can very much enhance the thermopower S(T) and the figure of merit ZT. At a small doping and U >>1 we find ZT >=100. Above Tμ, the electron-hole symmetry is restored and S(T) drops to small values. For U >1 and moderate doping, there is a broad temperature interval in which ZT >1, even though the electronic thermal conductivity and the effective Lorenz number are not small. In this regime, the phonons might be less adverse to ZT. Large ZT is also obtained for a three-dimensional cubic lattice. Similar effects could not be obtained with non-interacting electrons or a Fermi liquid. This work is supported by the NSF grant No. DMR-1006605. V.Z. acknowledges support by Croatian MZOS Grant No.0035-0352843-2849

  18. Spectral functions of lightly doped antiferromagnets using dressed hole operators

    SciTech Connect

    Riera, J.A.; Dagotto, E.

    1997-06-01

    Literature addressing the existence of hole pockets in experiments for the high-T{sub c} cuprates and in theoretical analysis of electronic models of correlated electrons is reviewed. It is argued that the issue is not conclusively resolved, both in theory and experiments. The apparently large Fermi surface observed in numerical studies of the doped Hubbard and t-J models suggests the presence of 1{minus}x carriers (with x the concentration of holes). However, this is in contradiction with results obtained in similar calculations for the Drude weight which scales with x at low doping. To address such a paradox, {ital dressed} operators are here used. Their spectral decomposition A({bold k},{omega}) is analyzed specially using the t-J model on ladders, but considering also chains and two-dimensional (2D) clusters. The results are contrasted against those obtained with the standard bare operators. It is concluded that substantial changes in the spectral weight can occur by replacing the bare hole creation operator by its dressed version. Apparently large Fermi surfaces can turn into small ones by working with quasiparticle (qp) operators that represent accurately the state of one hole. Thus, large Fermi surfaces in angle-resolved photoemission (ARPES), obtained by the sudden removal of an electron, may not be in contradiction with a visualization of the normal state of lightly doped antiferromagnets as composed of a gas of spin polarons with energies approximately obtained from the rigid band doping of the half-filled dispersion. The coexistence of a large Fermi surface in ARPES with, e.g., a holelike Hall coefficient seems possible in systems with strong correlations. In this paper the expression hole pocket is used as representing a large accumulation of spectral weight centered at {bold k}=({plus_minus}{pi}/2,{plus_minus}{pi}/2) generated by antiferromagnetic correlations in 2D clusters, or in analogous positions for ladders and chains. (Abstract Truncated)

  19. Bistable salt doped cholesteric liquid crystals light shutter

    NASA Astrophysics Data System (ADS)

    Moheghi, Alireza; Nemati, Hossein; Li, Yannian; Li, Quan; Yang, Deng-Ke

    2016-02-01

    Liquid crystals have been used to make electrically switchable light shutters (windows), but most of them are monostable: opaque in the absence of applied voltage and transparent when a voltage is applied. Here we report a bistable switchable light shutter based on cholesteric liquid crystal doped with tetrabutylammonium bromide. The salt makes it possible for the liquid crystal to have different electro-optical responses to applied voltages with different frequencies. The shutter can be either transparent or opaque in the absence of applied voltage. It can be switched from the transparent state to the opaque state by applying a low frequency (60 Hz) voltage pulse and switched back to the transparent state by applying a high frequency (2 kHz) voltage pulse. Because of the bistability, it can be used for energy-saving switchable privacy control and architectural windows.

  20. Slow light structures in dye-doped polymer waveguides

    NASA Astrophysics Data System (ADS)

    McKenna, Ed; Mickelson, Alan R.

    2007-07-01

    We present a simple and consistent technique for fabricating slow light structures in dye-doped polymer waveguides using the process of irreversible photobleaching. The slow light structures are moiré gratings. The gratings are holographically written into channel waveguides photobleached in side-chained PMMA/DR1 films. The films are annealed during the photobleaching process in order to remove stresses in the films generated during the photobleaching process. These stresses have been observed to cause distortion and cracking of the film surface. The slowing factor for the moiré gratings is calculated from the reflectance spectrum of the waveguides using the Hilbert transform. Moiré gratings with slowing factors between 1.6 and 2.6 are demonstrated.

  1. Fabrication of a dye-doped liquid crystal light shutter by thermal curing of polymer

    NASA Astrophysics Data System (ADS)

    Yu, Byeong-Hun; Ji, Seong-Min; Kim, Jin-Hun; Huh, Jae-Won; Yoon, Tae-Hoon

    2017-07-01

    We report a thermal curing method for fabrication of a dye-doped polymer-stabilized liquid crystal (PSLC) light shutter, which can prevent the decrease in absorption and discoloration of the dye caused by the UV curing process. We found that the measured transmittance in the opaque state of a dye-doped PSLC cell fabricated by thermal curing was approximately 35% lower than that of a dye-doped PSLC cell fabricated by UV curing. Thermal curing can be an alternative approach for fabrication of a dye-doped PSLC light shutter which can be used to provide high visibility of a see-through display.

  2. Synthesis and characterization of Sn-doped hematite as visible light photocatalyst

    SciTech Connect

    Cao, Zhiqin; Qin, Mingli; Gu, Yueru; Jia, Baorui; Chen, Pengqi; Qu, Xuanhui

    2016-05-15

    Highlights: • Sn-doped hematite nanoparticles are prepared by SCS in one step. • The Sn doping have the ability to inhibit particle growth of hematite. • Sn can enhance visible light harvesting and e{sup −}/h{sup +} separation. • Sn-doped hematite degrades MB under visible light effectively. • The products with 5 mol% Sn have the highest photocatalytic activity. - Abstract: Sn-doped hematite nanoparticles are prepared by solution combustion synthesis. The products are characterized with various analytical and spectroscopic techniques to determine their structural, morphological, light absorption and photocatalytic properties. The results reveal that all the samples consist of nanocrystalline hematite with mesoporous structures, and Sn has the ability to inhibit the growth of hematite particle. Compared to pure hematite, the doped hematite samples with appropriate amount of Sn show better activities for degradation of methylene blue under visible light irradiation. The highest activity is observed for 5% Sn doped hematite and this product has long-term stability and no selectivity for dye degradation. The enhanced performance of 5% Sn doped hematite is ascribed to the smaller particle size, increased ability to absorb in visible light, efficient charge separation as well as improved e{sup −} transfer associated with the effects of appropriate amount of Sn doped sample.

  3. Holon Wigner Crystal in a Lightly Doped Kagome Quantum Spin Liquid

    NASA Astrophysics Data System (ADS)

    Jiang, Hong-Chen; Devereaux, T.; Kivelson, S. A.

    2017-08-01

    We address the problem of a lightly doped spin liquid through a large-scale density-matrix renormalization group study of the t -J model on a kagome lattice with a small but nonzero concentration δ of doped holes. It is now widely accepted that the undoped (δ =0 ) spin-1 /2 Heisenberg antiferromagnet has a spin-liquid ground state. Theoretical arguments have been presented that light doping of such a spin liquid could give rise to a high temperature superconductor or an exotic topological Fermi liquid metal. Instead, we infer that the doped holes form an insulating charge-density wave state with one doped hole per unit cell, i.e., a Wigner crystal. Spin correlations remain short ranged, as in the spin-liquid parent state, from which we infer that the state is a crystal of spinless holons, rather than of holes. Our results may be relevant to kagome lattice herbertsmithite upon doping.

  4. A spatial interpretation of emerging superconductivity in lightly doped cuprates

    NASA Astrophysics Data System (ADS)

    Deutscher, Guy; de Gennes, Pierre-Gilles

    The formation of domains comprising alternating 'hole rich' and 'hole poor' ladders recently observed by Scanning Tunneling Microscopy by Kohsaka et al., on lightly hole doped cuprates, is interpreted in terms of an attractive mechanism which favors the presence of doped holes on Cu sites located each on one side of an oxygen atom. This mechanism leads to a geometrical pattern of alternating hole-rich and hole-poor ladders with a periodicity equal to 4 times the lattice spacing in the CuO plane, as observed experimentally. Cuprates supraconducteurs peu dopés : une interprétation des structures spatiales. Des arrangements électroniques réguliers ont été détectés récemment par Kohsaka et al. dans des cuprates sous dopés (via une sonde tunnel locale). Certaines paires Cu-O-Cu sont « actives », et forment une échelle. Les autres sites sont peu actifs. Pour expliquer ces structures, nous postulons que, lorsqu'une liaison Cu-O-Cu est occupée par deux trous, la distance (Cu-Cu) rétrécit et l'intégrale de transfert (t) est fortement augmentée. Ceci peut engendrer des paires localisées (réelles ou virtuelles). Aux taux de dopage étudiés, la période de répétition vaudrait 4 mailles élémentaires.

  5. Sb-doped p-ZnO /Ga-doped n-ZnO homojunction ultraviolet light emitting diodes

    NASA Astrophysics Data System (ADS)

    Chu, S.; Lim, J. H.; Mandalapu, L. J.; Yang, Z.; Li, L.; Liu, J. L.

    2008-04-01

    ZnO p-n homojunction light emitting diodes were fabricated based on p-type Sb-doped ZnO /n-type Ga-doped ZnO thin films. Low resistivity Au /NiO and Au /Ti contacts were formed on top of p-type and n-type ZnO layers, respectively. Au /NiO contacts on p-type ZnO exhibited a low specific resistivity of 7.4×10-4Ωcm2. The light emitting diodes yielded strong near-band-edge emissions in temperature-dependent and injection current-dependent electroluminescence measurements.

  6. Theoretical study of phosphorescence in dye doped light emitting diodes.

    PubMed

    Minaev, Boris; Jansson, Emil; Agren, Hans; Schrader, Sigurd

    2006-12-21

    Phosphorescence of platinum(II) octaethyl porphyrin (PtOEP), which has been used in organic light emitting diodes to overcome the efficiency limit imposed by the formation of triplet excitons, is studied by time-dependent (TD) density functional theory (DFT). The spin-orbit coupling (SOC) effects and the phosphorescence radiative lifetime (tau(p) (r)), calculated by the TD DFT method with the quadratic response technique, are analyzed for a series of porphyrins in order to elucidate the internal heavy atom effect on tau(p) (r). While the significance of the d(pi) orbital admixture into the lowest unoccupied molecular orbital e(g)(pi(*)), proposed by Gouterman et al. [J. Chem. Phys. 56, 4073 (1972)], is supported by our SOC calculations, we find that the charge-transfer (CT) mechanism is more important; the CT state of the (3)A(2g) symmetry provides effective SOC mixing with the ground state, and a large (3)A(2g)-(3)E(u) transition dipole moment gives the main contribution to the radiative phosphorescence rate constant. The IR and Raman spectra in the ground state and first excited triplet state (T(1)) are studied for proper assignment of vibronic patterns. An orbital angular momentum of the T(1) state is not quenched completely by the Jahn-Teller effect. A large zero-field splitting is predicted for PtP and PtOEP which results from a competition between the SOC and Jahn-Teller effects. A strong vibronic activity is found for the e(g) mode at 230 cm(-1) in PtP phosphorescence which is shifted to 260 cm(-1) in PtOEP. This out-of-plane vibration of the Pt atom produces considerable change of the SOC mixing. The role of charge-transfer state of d(pi)pi(*) type is stressed for the explanation of the electroluminescent properties of the dye doped light emitting diode.

  7. Theoretical study of phosphorescence in dye doped light emitting diodes

    NASA Astrophysics Data System (ADS)

    Minaev, Boris; Jansson, Emil; Ågren, Hans; Schrader, Sigurd

    2006-12-01

    Phosphorescence of platinum(II) octaethyl porphyrin (PtOEP), which has been used in organic light emitting diodes to overcome the efficiency limit imposed by the formation of triplet excitons, is studied by time-dependent (TD) density functional theory (DFT). The spin-orbit coupling (SOC) effects and the phosphorescence radiative lifetime (τpr), calculated by the TD DFT method with the quadratic response technique, are analyzed for a series of porphyrins in order to elucidate the internal heavy atom effect on τpr. While the significance of the dπ orbital admixture into the lowest unoccupied molecular orbital eg(π*), proposed by Gouterman et al. [J. Chem. Phys. 56, 4073 (1972)], is supported by our SOC calculations, we find that the charge-transfer (CT) mechanism is more important; the CT state of the A2g3 symmetry provides effective SOC mixing with the ground state, and a large A2g3-Eu3 transition dipole moment gives the main contribution to the radiative phosphorescence rate constant. The IR and Raman spectra in the ground state and first excited triplet state (T1) are studied for proper assignment of vibronic patterns. An orbital angular momentum of the T1 state is not quenched completely by the Jahn-Teller effect. A large zero-field splitting is predicted for PtP and PtOEP which results from a competition between the SOC and Jahn-Teller effects. A strong vibronic activity is found for the eg mode at 230cm-1 in PtP phosphorescence which is shifted to 260cm-1 in PtOEP. This out-of-plane vibration of the Pt atom produces considerable change of the SOC mixing. The role of charge-transfer state of dππ* type is stressed for the explanation of the electroluminescent properties of the dye doped light emitting diode.

  8. High drain current density and reduced gate leakage current in channel-doped AlGaN /GaN heterostructure field-effect transistors with Al2O3/Si3N4 gate insulator

    NASA Astrophysics Data System (ADS)

    Maeda, Narihiko; Wang, Chengxin; Enoki, Takatomo; Makimoto, Toshiki; Tawara, Takehiko

    2005-08-01

    Channel-doped AlGaN /GaN heterostructure field-effect transistors (HFETs) with metal-insulator-semiconductor (MIS) structures have been fabricated to obtain the high drain current density and reduced gate leakage current. A thin bilayer dielectric of Al2O3(4nm)/Si3N4(1nm) was used as the gate insulator, to simultaneously take advantage of the high-quality interface between Si3N4 and AlGaN, and high resistivity and a high dielectric constant of Al2O3. A MIS HFET with a gate length of 1.5μm has exhibited a record high drain current density of 1.87A/mm at a gate voltage (Vg) of +3V, which is ascribed to a high applicable Vg and a very high two-dimensional electron gas (2DEG) density of 2.6×1013cm-2 in the doped channel. The gate leakage current was reduced by two or three orders of magnitude, compared with that in normal HFETs without a gate insulator. The transconductance (gm) was 168mS/mm, which is high in the category of the MIS structure. Channel-doped MIS HFETs fabricated have thus been proved to exhibit the high current density, reduced gate leakage current, and relatively high transconductance, hence, promising for high-power applications.

  9. Ultraviolet light-emitting diodes with polarization-doped p-type layer

    NASA Astrophysics Data System (ADS)

    Hu, Wenxiao; Qin, Ping; Song, Weidong; Zhang, Chongzhen; Wang, Rupeng; Zhao, Liangliang; Xia, Chao; Yuan, Songyang; Yin, Yian; Li, Shuti

    2016-09-01

    We report ultraviolet light emitting diode (LEDs) with polarization doped p-type layer. Fabricated LEDs with polarization doped p-type layer exhibited reduced forward voltage and enhanced light output power, compared to those with traditional p-type AlGaN layer. The improvement is attributed to improved hole concentration and the smooth valence band by the polarization enhanced p-type doping. Our simulated results reveal that this p-type layer can further enhance the performance of ultraviolet LEDs by removing the electron blocking layer (EBL).

  10. Shape control of colloidal Mn doped ZnO nanocrystals and their visible light photocatalytic properties.

    PubMed

    Yang, Yefeng; Li, Yaguang; Zhu, Liping; He, Haiping; Hu, Liang; Huang, Jingyun; Hu, Fengchun; He, Bo; Ye, Zhizhen

    2013-11-07

    For colloidal semiconductor nanocrystals (NCs), shape control and doping as two widely applied strategies are crucial for enhancing and manipulating their functional properties. Here we report a facile and green synthetic approach for high-quality colloidal Mn doped ZnO NCs with simultaneous control over composition, shape and optical properties. Specifically, the shape of doped ZnO NCs can be finely modulated from three dimensional (3D) tetrapods to 0D spherical nanoparticles in a single reaction scheme. The growth mechanism of doped ZnO NCs with interesting shape transition is explored. Furthermore, we demonstrate the tunable optical absorption features of Mn doped ZnO NCs by varying the Mn doping levels, and the enhanced photocatalytic performance of Mn doped ZnO NCs under visible light, which can be further optimized by delicately controlling their shapes and Mn doping concentrations. Our results provide an improved understanding of the growth mechanism of doped NCs during the growth process and can be potentially extended to ZnO NCs doped with other metal ions for various applications.

  11. Light shutter using dichroic-dye-doped long-pitch cholesteric liquid crystals.

    PubMed

    Yu, Byeong-Hun; Huh, Jae-Won; Kim, Ki-Han; Yoon, Tae-Hoon

    2013-12-02

    We propose a light shutter device using dichroic-dye-doped liquid crystals (LCs) whose Bragg reflection wavelength is set to be infrared by controlling the pitch of cholesteric liquid crystals (ChLCs). A dye-doped long-pitch ChLC cell is switchable between the dark planar state and the transparent homeotropic state. It has the advantages of high transmittance, low operation voltage, and an easy fabrication process relative to previous LC light shutter devices. The proposed light shutter device is expected to achieve high visibility for transparent organic light-emitting diode displays and emerging smart windows, which can be used in airplanes, cars, and other similar applications.

  12. Room-temperature ferromagnetism in lightly Cr-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Duan, L. B.; Zhao, X. R.; Liu, J. M.; Wang, T.; Rao, G. H.

    2010-06-01

    Zn1- x Cr x O (0≤ x≤0.15) nanoparticles were synthesized by an auto-combustion method and characterized by x-ray diffraction and Raman scattering techniques. The solubility limit for Cr in ZnO was determined as x≈0.03. Room-temperature ferromagnetism (RT-FM) was observed in lightly Cr-doped ZnO nanoparticles with x=0.01 and 0.02. Raman scattering spectra of the lightly Cr-doped and Co-doped ZnO were studied and compared. The enhancement of both the magnetization and the intensity of Raman scattering peak associated with donor defects (Zni and/or VO) and carriers indicates that light Cr doping in ZnO could be an effective way to achieve pronounced RT-FM and the ferromagnetism is closely related to the dopant-donor hybridization besides the ferromagnetic Cr-O-Cr superexchange interactions.

  13. The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices

    SciTech Connect

    Cheon, Kwang-Ohk

    2003-01-01

    Organic light-emitting devices (OLEDs) constitute a new and exciting emissive display technology. In general, the basic OLED structure consists of a stack of fluorescent organic layers sandwiched between a transparent conducting-anode and metallic cathode. When an appropriate bias is applied to the device, holes are injected from the anode and electrons from the cathode; some of the recombination events between the holes and electrons result in electroluminescence (EL). Until now, most of the efforts in developing OLEDs have focused on display applications, hence on devices within the visible range. However some organic devices have been developed for ultraviolet or infrared emission. Various aspects of the device physics of doped small molecular OLEDs were described and discussed. The doping layer thickness and concentration were varied systematically to study their effects on device performances, energy transfer, and turn-off dynamics. Low-energy-gap DCM2 guest molecules, in either α-NPD or DPVBi host layers, are optically efficient fluorophores but also generate deep carrier trap-sites. Since their traps reduce the carrier mobility, the current density decreases with increased doping concentration. At the same time, due to efficient energy transfer, the quantum efficiency of the devices is improved by light doping or thin doping thickness, in comparison with the undoped neat devices. However, heavy doping induces concentration quenching effects. Thus, the doping concentration and doping thickness may be optimized for best performance.

  14. Lag and light-transfer characteristics of amorphous selenium photoconductive film with tellurium-doped layer

    NASA Astrophysics Data System (ADS)

    Park, Wug-Dong; Tanioka, Kenkichi

    2016-07-01

    Amorphous selenium (a-Se) high-gain avalanche rushing amorphous photoconductor (HARP) films have been used for highly sensitive imaging devices. To study a-Se HARP films for a solid-state image sensor, current-voltage, lag, spectral response, and light-transfer characteristics of 0.4-µm-thick a-Se HARP films are investigated. Also, to clarify a suitable Te-doped a-Se layer thickness in the a-Se photoconductor, we considered the effects of Te-doped layer thickness on the lag, spectral response, and light-transfer characteristics of 0.4-µm-thick a-Se HARP films. The threshold field, at which avalanche multiplication occurs in the a-Se HARP targets, decreases when the Te-doped layer thickness increases. The lag of 0.4-µm-thick a-Se HARP targets with Te-doped layers is higher than that of the target without Te doping. The lag of the targets with Te-doped layers is caused by the electrons trapped in the Te-doped layers within the 0.4-µm-thick a-Se HARP films. From the results of the spectral response measurement of about 15 min, the 0.4-µm-thick a-Se HARP targets with Te-doped layers of 90 and 120 nm are observed to be unstable owing to the electrons trapped in the Te-doped a-Se layer. From the light-transfer characteristics of 0.4-µm-thick a-Se HARP targets, as the slope at the operating point of signal current-voltage characteristics in the avalanche mode increases, the γ of the a-Se HARP targets decreases. Considering the effects of dark current on the lag and spectral response characteristics, a Te-doped layer of 60 nm is suitable for 0.4-µm-thick a-Se HARP films.

  15. Spin-on doping of germanium-on-insulator wafers for monolithic light sources on silicon

    NASA Astrophysics Data System (ADS)

    Al-Attili, Abdelrahman Z.; Kako, Satoshi; Husain, Muhammad K.; Gardes, Frederic Y.; Arimoto, Hideo; Higashitarumizu, Naoki; Iwamoto, Satoshi; Arakawa, Yasuhiko; Ishikawa, Yasuhiko; Saito, Shinichi

    2015-05-01

    High electron doping of germanium (Ge) is considered to be an important process to convert Ge into an optical gain material and realize a monolithic light source integrated on a silicon chip. Spin-on doping is a method that offers the potential to achieve high doping concentrations without affecting crystalline qualities over other methods such as ion implantation and in-situ doping during material growth. However, a standard spin-on doping recipe satisfying these requirements is not yet available. In this paper we examine spin-on doping of Ge-on-insulator (GOI) wafers. Several issues were identified during the spin-on doping process and specifically the adhesion between Ge and the oxide, surface oxidation during activation, and the stress created in the layers due to annealing. In order to mitigate these problems, Ge disks were first patterned by dry etching followed by spin-on doping. Even by using this method to reduce the stress, local peeling of Ge could still be identified by optical microscope imaging. Nevertheless, most of the Ge disks remained after the removal of the glass. According to the Raman data, we could not identify broadening of the lineshape which shows a good crystalline quality, while the stress is slightly relaxed. We also determined the linear increase of the photoluminescence intensity by increasing the optical pumping power for the doped sample, which implies a direct population and recombination at the gamma valley.

  16. Persistent spin excitations in doped antiferromagnets revealed by resonant inelastic light scattering

    NASA Astrophysics Data System (ADS)

    Jia, C. J.; Nowadnick, E. A.; Wohlfeld, K.; Kung, Y. F.; Chen, C.-C.; Johnston, S.; Tohyama, T.; Moritz, B.; Devereaux, T. P.

    2014-02-01

    How coherent quasiparticles emerge by doping quantum antiferromagnets is a key question in correlated electron systems, whose resolution is needed to elucidate the phase diagram of copper oxides. Recent resonant inelastic X-ray scattering (RIXS) experiments in hole-doped cuprates have purported to measure high-energy collective spin excitations that persist well into the overdoped regime and bear a striking resemblance to those found in the parent compound, challenging the perception that spin excitations should weaken with doping and have a diminishing effect on superconductivity. Here we show that RIXS at the Cu L3-edge indeed provides access to the spin dynamical structure factor once one considers the full influence of light polarization. Further we demonstrate that high-energy spin excitations do not correlate with the doping dependence of Tc, while low-energy excitations depend sensitively on doping and show ferromagnetic correlations. This suggests that high-energy spin excitations are marginal to pairing in cuprate superconductors.

  17. Superhydrophilicity-assisted preparation of transparent and visible light activated N-doped titania film

    NASA Astrophysics Data System (ADS)

    Xu, Qing Chi; Wellia, Diana V.; Amal, Rose; Liao, Dai Wei; Loo, Say Chye Joachim; Tan, Timothy Thatt Yang

    2010-07-01

    A novel and environmental friendly method was developed to prepare transparent, uniform, crack-free and visible light activated nitrogen doped (N-doped) titania thin films without the use of organic Ti precursors and organic solvents. The N-doped titania films were prepared from heating aqueous peroxotitanate thin films deposited uniformly on superhydrophilic uncoated glass substrates. The pure glass substrates were superhydrophilic after being heated at 500 °C for 1 h. Nitrogen concentrations in the titania films were adjusted by changing the amount of ammonia solution. The optimal photocatalytic activity of the N-doped titania films was about 14 times higher than that of a commercial self-cleaning glass under the same visible light illumination. The current reported preparative technique is generally applicable for the preparation of other thin films.

  18. Combining Microbial Enzyme Kinetics Models with Light Use Efficiency Models to Predict CO2 and CH4 Ecosystem Exchange from Flooded and Drained Peatland Systems

    NASA Astrophysics Data System (ADS)

    Oikawa, P. Y.; Jenerette, D.; Knox, S. H.; Sturtevant, C. S.; Verfaillie, J. G.; Baldocchi, D. D.

    2014-12-01

    Under California's Cap-and-Trade program, companies are looking to invest in land-use practices that will reduce greenhouse gas (GHG) emissions. The Sacramento-San Joaquin River Delta is a drained cultivated peatland system and a large source of CO2. To slow soil subsidence and reduce CO2 emissions, there is growing interest in converting drained peatlands to wetlands. However, wetlands are large sources of CH4 that could offset CO2-based GHG reductions. The goal of our research is to provide accurate measurements and model predictions of the changes in GHG budgets that occur when drained peatlands are restored to wetland conditions. We have installed a network of eddy covariance towers across multiple land use types in the Delta and have been measuring CO2 and CH4 ecosystem exchange for multiple years. In order to upscale these measurements through space and time we are using these data to parameterize and validate a process-based biogeochemical model. To predict gross primary productivity (GPP), we are using a simple light use efficiency (LUE) model which requires estimates of light, leaf area index and air temperature and can explain 90% of the observed variation in GPP in a mature wetland. To predict ecosystem respiration we have adapted the Dual Arrhenius Michaelis-Menten (DAMM) model. The LUE-DAMM model allows accurate simulation of half-hourly net ecosystem exchange (NEE) in a mature wetland (r2=0.85). We are working to expand the model to pasture, rice and alfalfa systems in the Delta. To predict methanogenesis, we again apply a modified DAMM model, using simple enzyme kinetics. However CH4 exchange is complex and we have thus expanded the model to predict not only microbial CH4 production, but also CH4 oxidation, CH4 storage and the physical processes regulating the release of CH4 to the atmosphere. The CH4-DAMM model allows accurate simulation of daily CH4 ecosystem exchange in a mature wetland (r2=0.55) and robust estimates of annual CH4 budgets. The LUE

  19. Dislocation associated incubational domain formation in lightly gadolinium-doped ceria.

    PubMed

    Li, Zhi-Peng; Mori, Toshiyuki; Ye, Fei; Ou, Ding Rong; Zou, Jin; Drennan, John

    2011-02-01

    Nanosized incubational domain was observed in 10 at.% gadolinium-doped ceria (GDC) using high-resolution transmission electron microscopy. Dislocations were extensively observed in 10 at.% GDC instead of heavily doped 25 at.% GDC. By Fast Fourier Transform and Inverse Fast Fourier Transform analysis, it was noticed that the incubational domain existing in 10 at.% GDC has different lattice spacing and orientation from the neighboring ceria matrix. Furthermore, dislocations were usually observed in the interface region between the incubational domain and the ceria matrix. Based on experimental results, the formation mechanism of dislocation associated incubational domain in lightly gadolinium-doped ceria is rationalized.

  20. Incident light dependence for photocatalytic degradation of acetaldehyde and acetic acid on S-doped and N-doped TiO 2 photocatalysts

    NASA Astrophysics Data System (ADS)

    Nishijima, Kazumoto; Ohtani, Bunsho; Yan, Xiaoli; Kamai, Taka-aki; Chiyoya, Tetsuo; Tsubota, Toshiki; Murakami, Naoya; Ohno, Teruhisa

    2007-10-01

    We have synthesized S (S 4+)-doped and N (N 3-)-doped TiO 2 photocatalysts. S-doped and N-doped TiO 2 loaded with Fe 2O 3 nanoparticles have also been prepared. These photocatalysts showed activity under a wide range of wavelengths of irradiation. Action spectra of photochemical reaction rate as a function of the incident light wavelength for oxidation of acetic acid on S-doped TiO 2 was studied.The photocatalytic activities of S-doped and N-doped TiO 2 photocatalysts loaded with Fe 2O 3 nanoparticles for oxidation of acetic acid in aqueous phase and acetaldehyde in gas phase are markedly improved compared to those of doped TiO 2 without loading of Fe 2O 3 nanoparticles under a wide range of incident light wavelengths. The optimum amount of Fe 2O 3 nanoparticles loaded on S-doped TiO 2 particles was different from that on N-doped TiO 2 for oxidation of organic compounds. The relationship between reaction rate of photocatalytic oxidation of acetaldehyde on doped TiO 2 loaded with Fe 2O 3 nanoparticles and amount of Fe 2O 3 nanoparticles is discussed.

  1. Poor electronic screening in lightly doped Mott insulators observed with scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Battisti, I.; Fedoseev, V.; Bastiaans, K. M.; de la Torre, A.; Perry, R. S.; Baumberger, F.; Allan, M. P.

    2017-06-01

    The effective Mott gap measured by scanning tunneling microscopy (STM) in the lightly doped Mott insulator (Sr1-xLax) 2IrO4 differs greatly from values reported by photoemission and optical experiments. Here we show that this is a consequence of the poor electronic screening of the tip-induced electric field in this material. Such effects are well known from STM experiments on semiconductors and go under the name of tip-induced band bending (TIBB). We show that this phenomenon also exists in the lightly doped Mott insulator (Sr1-xLax) 2IrO4 and that, at doping concentrations of x ≤4 % , it causes the measured energy gap in the sample density of states to be bigger than the one measured with other techniques. We develop a model able to retrieve the intrinsic energy gap leading to a value which is in rough agreement with other experiments, bridging the apparent contradiction. At doping x ≈5 % we further observe circular features in the conductance layers that point to the emergence of a significant density of free carriers in this doping range and to the presence of a small concentration of donor atoms. We illustrate the importance of considering the presence of TIBB when doing STM experiments on correlated-electron systems and discuss the similarities and differences between STM measurements on semiconductors and lightly doped Mott insulators.

  2. Rotation sensing with Er3+-doped active ring resonator slow light structure

    NASA Astrophysics Data System (ADS)

    Gu, Hong; Liu, Xiaoqin

    2016-10-01

    An optical gyroscope, which is constituted by Er3+-doped active ring resonator (EDARR) slow light structure, is presented for the first time. The principle of improving the sensitivity of the detection of angular velocity is analysed in detail. The expression of the rotation phase difference of EDARR between the counter-propagating waves is derived and discussed. At the resonant frequency, the phase shift difference has the maximum value when the light power in the cavity is far greater than the input light power. We designed an experimental scheme of Er3+-doped active ring resonator slow light system. Two additional bias phases ϕb = ±π/2 were introduced in the optical path, by recording the light intensity difference ? and I0 at the resonant frequency ?, the input angular velocity can be obtained. The slow light structure based on EDARR can enhance the sensitivity of the detection of the angular velocity by three orders of magnitude.

  3. Drain vs No Drain After Colorectal Surgery.

    PubMed

    Tsujinaka, Shingo; Konishi, Fumio

    2011-03-01

    In colorectal surgery, drains are expected to prevent hematoma, fluid collection, or abscess formation, to act as an indicator of postoperative complication, or to minimize the severity of complication-related symptoms. Routine drainage has not been advocated by meta-analyses as they failed to demonstrate any benefit in reducing anastomotic leak rate, minimizing symptoms, or serving as a warning function. Moreover, some reports even showed that drain itself is an independent risk factor of anastomosis. The introduction of total mesorectal excision (TME) for rectal cancer surgery has given further concern to this controversial issue, that the use of drain decreased anastomotic failure rate and the need for surgical re-intervention. While controversy still remains, the choice of using drain is left to the individual surgeon's preference in daily practice. Therefore, surgeons should be well acquainted with purpose of drainage (prophylaxis, information, or treatment), characteristics (materials), clinical application of drain (type of drainage system, timing of removal), surgical outcomes after using drain (incidence of postoperative complication), and drain-related complications. If drains are used, careful observation with proper use is crucial for the management. It is important that the duration of drainage should not be inadequately extended. Any complications directly associated with the use of drain should be avoided. New concepts of drain have been proposed as diagnostic tool using biomarkers, and as preventive device against anastomotic leak. This article overviews the available, published data on the use of drain in colorectal surgery.

  4. Visible-Light Activities of Erbium Doped BiVO4 Photocatalysts

    NASA Astrophysics Data System (ADS)

    Zhang, Ai-ping; Zhang, Jin-zhi

    2010-02-01

    Er-doped BiVO4 composite photocatalyst was hydrothermal synthesized and characterized by X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray Spectroscopy, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectra techniques. The activity of the catalyst was determined by oxidative decomposition of methyl orange in aqueous solution under visible-light irradiation. X-ray photoelectron spectroscopy and energy-dispersive X-ray Spectroscopy analysis revealed that the doped Er existed in the form of Er2O3. It also showed that the Er doping can enhance the visible-light absorption abilities of catalysts and their visible-light-driven photocatalytic activities in comparison with those of pure BiVO4.

  5. Photocatalytic activity of Fe-doped CaTiO₃ under UV-visible light.

    PubMed

    Yang, He; Han, Chong; Xue, Xiangxin

    2014-07-01

    The photocatalytic degradation of methylene blue (MB) over Fe-doped CaTiO₃ under UV-visible light was investigated. The as-prepared samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) system, Fourier transform infrared spectra (FT-IR), and UV-visible diffuse reflectance spectroscopy (DRS). The results show that the doping with Fe significantly promoted the light absorption ability of CaTiO₃ in the visible light region. The Fe-doped CaTiO₃ exhibited higher photocatalytic activity than CaTiO₃ for the degradation of MB. However, the photocatalytic activity of the Fe-doped CaTiO₃ was greatly influenced by the calcination temperature during the preparation process. The Fe-doped CaTiO₃ prepared at 500°C exhibited the best photocatalytic activity, with degradation of almost 100% MB (10ppm) under UV-visible light for 180 min.

  6. A controllable growth-doping approach to synthesize bright white-light-emitting Cd:In2S3 nanocrystals.

    PubMed

    Feng, Jian; Zhu, Hui; Yang, Xiurong

    2013-07-21

    A new type of doped Cd:In2S3 NC, which exhibits bright white-light emission with a QY of about 18%, synthesized by a one-pot G-doping synthesis approach is presented. The successful realization of temporal separation of nucleation doping and growth doping makes this approach a facile method to synthesize the In2S3/Cd:In2S3 core/shell nanostructure.

  7. Synthesis of plasmonic Ti(3+) doped Au/Cl-TiO2 mesocrystals with enhanced visible light photocatalytic activity.

    PubMed

    Yu, Xin; Fan, Xiaoli; Li, Zhonghua; Liu, Jiawen

    2017-09-12

    We successfully synthesized willow leaf-like plasmonic Ti(3+) doped Au/Cl-TiO2 mesocrystals by facile modified two-phase vapor hydrolysis and photoreduction methods. In this work, the as-prepared Ti(3+) doped TiO2 mesocrystals showed an interesting visible light harvesting capacity and visible light photocatalytic activity for hydrogen production. The plasmonic Ti(3+) doped Au/Cl-TiO2 mesocrystals also showed highly enhanced visible light absorption and visible light photocatalytic activity for hydrogen production, and the highest visible light photocatalytic activity reached 480.1 μmol g(-1) h(-1), which was 208.70 times as high as that of P25 TiO2 and 1.59 times as high as that of Ti(3+) doped TiO2 mesocrystals. Finally, the possible visible light photocatalytic mechanisms of plasmonic Ti(3+) doped Au/Cl-TiO2 mesocrystals for hydrogen production were proposed.

  8. Visible light photocatalytic antibacterial activity of Ni-doped and N-doped TiO2 on Staphylococcus aureus and Escherichia coli bacteria.

    PubMed

    Ananpattarachai, Jirapat; Boonto, Yuphada; Kajitvichyanukul, Puangrat

    2016-03-01

    The Ni-doped and N-doped TiO2 nanoparticles were investigated for their antibacterial activities on Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria. Their morphological features and characteristics such as particle size, surface area, and visible light absorbing capacity were compared and discussed. Scanning electron microscopy, X-ray diffraction, and UV-visible spectrophotometry were used to characterize both materials. The inactivation of E. coli (as an example of Gram-negative bacteria) and S. aureus (as an example of Gram-positive bacteria) with Ni-doped and N-doped TiO2 was investigated in the absence and presence of visible light. Antibacterial activity tests were conducted using undoped, Ni-doped, and N-doped TiO2. The N-doped TiO2 nanoparticles show higher antibacterial activity than Ni-doped TiO2. The band gap narrowing of N-doped TiO2 can induce more visible light absorption and leads to the superb antibacterial properties of this material. The complete inactivation time for E. coli at an initial cell concentration of 2.7 × 10(4) CFU/mL was 420 min which is longer than the 360 min required for S. aureus inactivation. The rate of inactivation of S. aureus using the doped TiO2 nanoparticles in the presence of visible light is greater than that of E. coli. The median lethal dose (LD50) values of S. aureus and E. coli by antibacterial activity under an 18-W visible light intensity were 80 and 350 mg/ml for N-doped TiO2, respectively.

  9. Fermi energy tuning with light to control doping profiles during epitaxy

    SciTech Connect

    Sanders, C. E.; Beaton, D. A.; Reedy, R. C.; Alberi, K.

    2015-05-04

    The influence of light stimulation and photogenerated carriers on the process of dopant surface segregation during growth is studied in molecular beam epitaxially grown Si-doped GaAs structures. The magnitude of surface segregation decreases under illumination by above-bandgap photons, wherein splitting of the quasi Fermi levels reduces the band bending at the growth surface and raises the formation energy of compensating defects that can enhance atomic diffusion. We further show that light-stimulated epitaxy can be used as a practical approach to diminish dopant carry-forward in device structures and improve the performance of inverted modulation-doped quantum wells.

  10. Holon Wigner Crystal in a Lightly Doped Kagome Quantum Spin Liquid

    DOE PAGES

    Jiang, Hong -Chen; Devereaux, T.; Kivelson, S. A.

    2017-08-07

    We address the problem of a lightly doped spin liquid through a large-scale density-matrix renormalization group study of the t–J model on a kagome lattice with a small but nonzero concentration δ of doped holes. It is now widely accepted that the undoped (δ = 0) spin-1/2 Heisenberg antiferromagnet has a spin-liquid ground state. Theoretical arguments have been presented that light doping of such a spin liquid could give rise to a high temperature superconductor or an exotic topological Fermi liquid metal. Instead, we infer that the doped holes form an insulating charge-density wave state with one doped hole permore » unit cell, i.e., a Wigner crystal. Spin correlations remain short ranged, as in the spin-liquid parent state, from which we infer that the state is a crystal of spinless holons, rather than of holes. In conclusion, our results may be relevant to kagome lattice herbertsmithite upon doping.« less

  11. Nitrogen doping of nanoporous WO3 layers by NH3 treatment for increased visible light photoresponse.

    PubMed

    Nah, Yoon-Chae; Paramasivam, Indhumati; Hahn, Robert; Shrestha, Nabeen K; Schmuki, Patrik

    2010-03-12

    Nanoporous WO(3) layers were grown by electrochemical anodization of W in a fluoride containing electrolyte. These layers were exposed to a thermal treatment in NH(3) to achieve nitrogen doping of the material. The morphology, crystal structure, composition and photoresponse of pure and nitrogen doped WO(3) were compared using scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and photoelectrochemical measurements. The results clearly show that successful nitrogen doping into WO(3) layers can be achieved by controlling the temperature and time during the NH(3) treatment. Most importantly, it is demonstrated that for the nitrogen doped WO(3) layers the photocurrent is significantly enhanced in the visible light region.

  12. Facile synthesis of phosphorus doped graphitic carbon nitride polymers with enhanced visible-light photocatalytic activity

    SciTech Connect

    Zhang, Ligang; Chen, Xiufang; Guan, Jing; Jiang, Yijun; Hou, Tonggang; Mu, Xindong

    2013-09-01

    Graphical abstract: - Highlights: • P-doped g-C{sub 3}N{sub 4} has been prepared by a one-pot green synthetic approach. • The incorporation of P resulted in favorable textural and electronic properties. • Doping with P enhanced the visible-light photocatalytic activity of g-C{sub 3}N{sub 4}. • A postannealing treatment further enhanced the activity of P-doped g-C{sub 3}N{sub 4}. • Photogenerated holes were the main species responsible for the activity. - Abstract: Phosphorus-doped carbon nitride materials were prepared by a one-pot green synthetic approach using dicyandiamide monomer and a phosphorus containing ionic liquid as precursors. The as-prepared materials were subjected to several characterizations and investigated as metal-free photocatalysts for the degradation of organic pollutants (dyes like Rhodamine B, Methyl orange) in aqueous solution under visible light. Results revealed that phosphorus-doped carbon nitride have a higher photocatalytic activity for decomposing Rhodamine B and Methyl orange in aqueous solution than undoped g-C{sub 3}N{sub 4}, which was attributed to the favorable textural, optical and electronic properties caused by doping with phosphorus heteroatoms into carbon nitride host. A facile postannealing treatment further improved the activity of the photocatalytic system, due to the higher surface area and smaller structural size in the postcalcined catalysts. The phosphorus-doped carbon nitride showed high visible-light photocatalytic activity, making them promising materials for a wide range of potential applications in photochemistry.

  13. Red-light emission induced by Mn-doped magnesium fluorogermanate

    NASA Astrophysics Data System (ADS)

    He, Jiabei; Li, Hao-Bo; Yuan, Linlin; Wang, Changhong; Cheng, Yahui; Wang, Wei-Hua; Lu, Feng; Li, Lan; Wang, Weichao; Liu, Hui

    2015-12-01

    As a potential red-light source in the white light emitting diodes (LEDs), Mn-doped magnesium fluorogermanate (Mg28Ge7.5O38F10) are investigated by the first principles calculation with the Heyd-Scuseria-Ernzerhof (HSE) functional. The results demonstrate that the neutral Mn substitutions at the Mg (Mn{{}\\text{Mg}} ), octahedral Ge (Mn{{}\\text{Ge≤ft(\\text{oct}\\right)}} ) and tetrahedral Ge (Mn{{}\\text{Ge≤ft(\\text{tet}\\right)}} ) sites are all energetically favorable. However, only Mn{{}\\text{Mg}} could create proper transition levels leading to the experimentally observed red-light emission under near ultra-violet (UV) excitation. Our results provide fundamental understanding of the Mn defects behavior and the corresponding red-light emission in Mn-doped magnesium fluorogermanate.

  14. Light non-metallic atom (B, N, O and F)-doped graphene: a first-principles study.

    PubMed

    Wu, M; Cao, C; Jiang, J Z

    2010-12-17

    First-principles calculations are performed to study the geometry, electronic structure and magnetic properties of light non-metallic atom-doped graphene (B, N, O and F). The planar structure and the quasi-linear energy dispersion near the Dirac point remain through doping with B and N atoms, by which p-type doping and n-type doping graphene are respectively induced. A bandgap of about 0.5 eV is generated through O doping, and geometrically the O atom is also in the graphene plane. No magnetic moment is detected in B- , N- and O-doped graphene. For F doping, the F atom bonds with one of the carbon atoms close to the vacancy, with the other two carbon atoms undergoing a Jahn-Teller distortion. A weak polarized magnetic moment of 0.71 µ(B) is detected through F doping.

  15. A QVGA-size CMOS time-of-flight range image sensor with background light charge draining structure

    NASA Astrophysics Data System (ADS)

    Ushinaga, Takeo; Halin, Izhal Abdul; Sawada, Tomonari; Kawahito, Shoji; Homma, Mitsuru; Maeda, Yasunari

    2006-02-01

    3-D imaging systems can be used in a variety of applications such as in automobile, medicine, robot vision systems, security and so on. Recently many kinds of range finding methods have been proposed for 3-D imaging systems. This paper presents a new type of CMOS range image sensor based on the Time-of-Flight (TOF)principle with a spatial resolution of 336 × 252 (QVGA) and pixels of 15 × 15 μm2 size. A pixel structure of the sensor consists of single layer polysilicon gates on thick field oxide and has a function of background light induced charge reduction. The chip was fabricated in a 0.35 μm standard CMOS process with two poly and three metal layers. The presented sensor achieves a minimum range resolution of 2.8cm at framerate of 30fps and the resolution is improved to 4.2mm for 10 frames averaging, which corresponds to 3fps.

  16. Formation of temperature fields in doped anisotropic crystals under spatially inhomogeneous light beams passing through them

    SciTech Connect

    Zaitseva, E. V.; Markelov, A. S.; Trushin, V. N. Chuprunov, E. V.

    2013-12-15

    The features of formation of thermal fields in potassium dihydrophosphate crystal doped with potassium permanganate under a 532-nm laser beam passing through it have been investigated. Data on the influence of birefringence on the temperature distribution in an anisotropic crystal whose surface is illuminated by a spatially modulated light beam are presented.

  17. Visible light induced photobleaching of methylene blue over melamine-doped TiO2 nanocatalyst

    EPA Science Inventory

    TiO2 doping with N-rich melamine produced a stable, active and visible light sentisized nanocatalyst that showed a remarkable efficiency towards the photobleaching of a model compound – methylene blue (MB) in aqueous solution. The photobleaching followed a mixed reaction order ki...

  18. Light-controllable reflection wavelength of blue phase liquid crystals doped with azobenzene-dimers.

    PubMed

    Chen, Xingwu; Wang, Ling; Li, Chenyue; Xiao, Jiumei; Ding, Hangjun; Liu, Xin; Zhang, Xiaoguang; He, Wanli; Yang, Huai

    2013-10-03

    A new series of azobenzene-dimers were synthesized and doped into the blue phase liquid crystals to broaden the temperature range of BPs. It is found that not only can the reflection wavelength of BPI be reversibly controlled but BPI can also be transformed into the cholesteric phase owing to isomerization of azobenzene induced by light.

  19. Visible light induced photobleaching of methylene blue over melamine-doped TiO2 nanocatalyst

    EPA Science Inventory

    TiO2 doping with N-rich melamine produced a stable, active and visible light sentisized nanocatalyst that showed a remarkable efficiency towards the photobleaching of a model compound – methylene blue (MB) in aqueous solution. The photobleaching followed a mixed reaction order ki...

  20. Effect of co-doping and tri-doping with transition metals and a nonmetal on photocatalytic activity in visible light of TiO2 thin film

    NASA Astrophysics Data System (ADS)

    Phung, Hang Nguyen Thai; Tran, Van Nguyen Khanh; Duong, Phuong Ai; Le, Hung Vu Tuan; Truong, Nguyen Duc

    2017-06-01

    Mono, co- and tri-doped TiO2 thin films with the transition metals (vanadium and/or chrominium) and a nonmetal (nitrogen) have been fabricated by sol-gel method. X-ray diffraction results clearly reveal anatase crystal structure for all obtained samples and doping with any dopants doesn't change the anatase phase of TiO2. Compared to TiO2, three types of doped TiO2 thin films exhibit a red-shift in the absorption edge and have much better photocatalytic properties for methylene blue degradation in visible light region. The maximum visible-photocatalytic performance was achieved for tri-doped TiO2 sample. The mechanism for enhancing visible-photocatalytic activity of co-doped and tri-doped TiO2 thin films was also examined.

  1. Electrochemical doping and the optical properties of light-emitting polymer materials and devices

    NASA Astrophysics Data System (ADS)

    Leger, Janelle Maureen

    The first three chapters of this dissertation serve as an introduction to the field of light-emitting polymers and polymer-based devices including materials, device construction, and measurement techniques. In chapter one I discuss the physical models necessary to understand semiconductivity in conjugated polymers. Chapter two reviews the device physics of several important applications. In chapter three I introduce the experimental techniques used in the following studies. Two well established light-emitting polymer devices include the polymer LED and the polymer LEC. The LEC uses electrochemical doping to achieve the charge injection necessary for light emission, while the LED injects charge directly from contact electrodes. I use a technique employing simulations of interference effects in multilayered device structures, matching experimental device spectra to simulation in order to gain insight into the location of light emission within the device. In chapter four I use this technique to explore the thickness dependence of PLEDs. In chapter five I combine simulations of interference effects in LECs with studies of planar geometry devices, thereby providing information about the fundamental operating mechanism of these devices. Several polymer-based applications include light-emitting electrochemical cells (LEC), electrochromic devices (ECD), and actuators, for which the operating mechanism depends heavily on electrochemical doping. Unfortunately, the doping of light-emitting polymers is not well understood. In chapter six I study the basic electrochemical doping reactions of one common light-emitting polymer, MEH-PPV. I explore factors affecting the fundamental doping reaction through cyclic voltammetry. Further, I investigate the optical properties of doped films in order to gain insight into the structural changes and changes in the energy band structure induced by doping. Finally, I explore some unique functionalities of MEH-PPV, specifically electrochromic

  2. A study on the band gap and the doping level of V-doped TiO2 with respect to the visible-light photocatalytic activity.

    PubMed

    Choi, Ah Young; Han, Chul-Hee

    2014-10-01

    The visible-light response is a necessary but not a sufficient condition for semiconductor photocatalyst to function as a visible-light active photocatalyst. To shed more light on the issue of visible-light response of semiconductor photocatalysts, the band-gaps and the doping levels of multivalency vanadium-doped TiO2 were investigated from sonochemically prepared samples. Sonochemical doping, which relies on acoustic cavitation phenomena, is a one step process excluding chemical synthesis, and three types of vanadium doped TiO2 nanopowder were prepared using such vanadium oxides as V2O3, V2O4, and V2O5. The band-gaps of as-prepared samples were obtained from the diffuse reflectance measurement, and the doping levels of vanadium in these samples were measured using electron probe micro analyzer. In addition, X-ray photoelectron spectrometer was introduced to complement electron probe micro analyzer. Furthermore, quantum-chemical calculations on simple cluster models for TiO2 and V-doped TiO2 were performed, and the resulting computational results in conjunction with experimental findings provided valuable information on oxygen vacancy and doping mechanism.

  3. Tin doping speeds up hole transfer during light-driven water oxidation at hematite photoanodes.

    PubMed

    Dunn, Halina K; Feckl, Johann M; Müller, Alexander; Fattakhova-Rohlfing, Dina; Morehead, Samuel G; Roos, Julian; Peter, Laurence M; Scheu, Christina; Bein, Thomas

    2014-11-28

    Numerous studies have shown that the performance of hematite photoanodes for light-driven water splitting is improved substantially by doping with various metals, including tin. Although the enhanced performance has commonly been attributed to bulk effects such as increased conductivity, recent studies have noted an impact of doping on the efficiency of the interfacial transfer of holes involved in the oxygen evolution reaction. However, the methods used were not able to elucidate the origin of this improved efficiency, which could originate from passivation of surface electron-hole recombination or catalysis of the oxygen evolution reaction. The present study used intensity-modulated photocurrent spectroscopy (IMPS), which is a powerful small amplitude perturbation technique that can de-convolute the rate constants for charge transfer and recombination at illuminated semiconductor electrodes. The method was applied to examine the kinetics of water oxidation on thin solution-processed hematite model photoanodes, which can be Sn-doped without morphological change. We observed a significant increase in photocurrent upon Sn-doping, which is attributed to a higher transfer efficiency. The kinetic data obtained using IMPS show that Sn-doping brings about a more than tenfold increase in the rate constant for water oxidation by photogenerated holes. This result provides the first demonstration that Sn-doping speeds up water oxidation on hematite by increasing the rate constant for hole transfer.

  4. Doping Evolution and Junction Formation in Stacked Cyanine Dye Light-Emitting Electrochemical Cells.

    PubMed

    Jenatsch, Sandra; Wang, Lei; Bulloni, Matia; Véron, Anna C; Ruhstaller, Beat; Altazin, Stéphane; Nüesch, Frank; Hany, Roland

    2016-03-01

    Cyanine dyes are fluorescent organic salts with intrinsic conductivity for ionic and electronic charges. Recently ( J. Am. Chem. Soc. 2013 , 135 , 18008 - 18011 ), these features have been exploited in cyanine light-emitting electrochemical cells (LECs). Here, we demonstrate that stacked, constant-voltage driven trimethine cyanine LECs with various counteranions develop a p-i-n junction that is composed of p- and n-doped zones and an intrinsic region where light-emission occurs. We introduce a method that combines spectral photocurrent response measurements with optical modeling and find that at maximum current the intrinsic region is centered at ∼37% away from the anode. Transient capacitance, photoluminescence and attenuance experiments indicate a device situation with a narrow p-doped region, an undoped region that occupies ∼72% of the dye layer thickness and an n-doped region with a maximum doping concentration of 0.08 dopant/cyanine molecule. Finally, we observe that during device relaxation the parent cyanines are not reformed. We ascribe this to irreversible reactions between doped cyanine radicals. For sterically conservative cyanine dyes, this suggests that undesired radical decomposition pathways limit the LEC long-term stability in general.

  5. Enhanced visible light photocatalytic degradation of Rhodamine B over phosphorus doped graphitic carbon nitride

    NASA Astrophysics Data System (ADS)

    Chai, Bo; Yan, Juntao; Wang, Chunlei; Ren, Zhandong; Zhu, Yuchan

    2017-01-01

    Phosphorus doped graphitic carbon nitride (g-C3N4) was easily synthesized using ammonium hexafluorophosphate (NH4PF6) as phosphorus source, and ammonium thiocyanate (NH4SCN) as g-C3N4 precursor, through a direct thermal co-polycondensation procedure. The obtained phosphorus doped g-C3N4 was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), UV-vis diffuse reflectance absorption spectra (UV-DRS), photoelectrochemical measurement and photoluminescence spectra (PL). The photocatalytic activities of phosphorus doped g-C3N4 samples were evaluated by degradation of Rhodamine B (RhB) solution under visible light irradiation. The results showed that the phosphorus doped g-C3N4 had a superior photocatalytic activity than that of pristine g-C3N4, attributing to the phosphorus atoms substituting carbon atoms of g-C3N4 frameworks to result in light harvesting enhancement and delocalized π-conjugated system of this copolymer, beneficial for the increase of photocatalytic performance. The photoelectrochemical measurements also verified that the charge carrier separation efficiency was promoted by phosphorus doping g-C3N4. Moreover, the tests of radical scavengers demonstrated that the holes (h+) and superoxide radicals (rad O2-) were the main active species for the degradation of RhB.

  6. Photoelectrolysis of water under visible light with doped SrTiO3 electrodes

    NASA Astrophysics Data System (ADS)

    Matsumura, M.; Hiramoto, M.; Tsubomura, H.

    1983-02-01

    The photochemical behavior of strontium titanate (SrTiOe) sintered electrodes doped with various metal oxides is reported, with reference to the development of semiconductor electrodes applicable in solar energy conversion. The doped semiconductor electrodes were synthesized from 99.9% pure SrTiO3 powder mixed with reagent grade metal oxide which was then pressed into disks of 1 cm in diameter and sintered at 400 C for 2 hr. From the I-V and other characteristic curves which were plotted for various wavelengths, the energy level of the surface state of SrTiO3 electrode is estimated to lie at 1.9 eV below the conduction band. The SrTiO3 electrodes doped with RuO2, V2O5, Cr2O3, Ce2O3, CoO, and Rh2O3 showed photoresponse in visible light, while undoped SrTiO3 and those electrodes doped with other metal oxides such as ZnO and Al2O3 were photosensitive only in UV light. The electroluminescence spectra of the doped electrodes are classified into three groups: those that have electroluminescence characteristics similar to those of the undoped electrodes, those with very intense and narrow luminescence bands in the visible region, and those that exhibit a broad band at wavelengths shorter than those of the undoped electrodes

  7. Near UV excitable yellow light emitting Zn doped MgO for WLED application

    NASA Astrophysics Data System (ADS)

    Vasanthi, V.; Kottaisamy, M.; Anitha, K.; Ramakrishnan, V.

    2017-06-01

    Nanoparticles of Mg1-xZnxO (x = 0, 0.05, 0.1, 0.15) were synthesized by sol-gel assisted combustion method and their optical properties has been investigated. Crystal structure, phase purity and doping of Zn2+ ions in MgO are confirmed from Powder X-ray diffraction method. Spherical shape porous particles are found with increasing particle density as a function of doping concentration. Doping of Zn ions in MgO has altered the optical band gap of MgO and reduced the band gap from 4.6 eV to 3.9 eV as the concentration of Zn increases. The optical absorption bands are observed in the visible region exhibited the presence of various defects such as F, F+, F2+ in MgO and these defects concentration increases with Zn doping. The photoluminescence emission spectra of Zn doped MgO shows a bright bluish green emission which starts from 450 nm to 570 nm and this light can be obtained at the excitation of near UV light from 330 to 380 nm. However, the same defective structure has led to a highly intense broad band emission which starts from 450 nm to 750 nm at the excitation of near UV LED (at 375 nm). This material can be used as a yellow emitting phosphor for phosphor converted white LEDs (PCWLEDs) at the excitation of near UV LEDs.

  8. Nitrogen-fluorine co-doped titania inverse opals for enhanced solar light driven photocatalysis

    NASA Astrophysics Data System (ADS)

    Rahul, T. K.; Sandhyarani, N.

    2015-10-01

    Three dimensionally ordered nitrogen-fluorine (N-F) co-doped TiO2 inverse opals (IOs) were fabricated by templating with polystyrene (PS) colloidal photonic crystals (CPCs) by infiltration. During preparation, the TiO2 precursor was treated with a mixture of nitric acid and trifluoroacetic acid to facilitate N-F co-doping into the TiO2 lattice. Enhanced solar light absorption was observed in the samples as a consequence of the red shift in the electronic band gap of TiO2 due to N-F co-doping. The photonic band gap (PBG) of these TiO2 IO films was tuned by varying the sphere size of the PS CPC templates. The as-prepared N-F co-doped TiO2 IO films were used as photocatalysts for the degradation of Rhodamine B (RhB) dye under solar light irradiation. A significant enhancement in the photocatalytic activity was observed in N-F co-doped TiO2 IO films prepared using PS spheres of 215 nm as a template, with the red edge of the PBG closer to the electronic band gap (EBG) of TiO2. 100% of the dye molecules were degraded within 2 minutes under direct solar irradiation, which is one of the fastest reaction times ever reported for RhB degradation in the presence of TiO2 photocatalysts. The N-F co-doped TiO2 IO film prepared using PS of 460 nm with its PBG centered at 695 nm also showed good photocatalytic activity. It was found that the IO films displayed improved photocatalytic activity in comparison to ordinary nanocrystalline (nc)-TiO2 films. The enhancement could be attributed to the bandgap scattering effect and the slow photon effect, leading to a significant improvement in solar light harvesting.

  9. Nitrogen-fluorine co-doped titania inverse opals for enhanced solar light driven photocatalysis.

    PubMed

    Rahul, T K; Sandhyarani, N

    2015-11-21

    Three dimensionally ordered nitrogen-fluorine (N-F) co-doped TiO2 inverse opals (IOs) were fabricated by templating with polystyrene (PS) colloidal photonic crystals (CPCs) by infiltration. During preparation, the TiO2 precursor was treated with a mixture of nitric acid and trifluoroacetic acid to facilitate N-F co-doping into the TiO2 lattice. Enhanced solar light absorption was observed in the samples as a consequence of the red shift in the electronic band gap of TiO2 due to N-F co-doping. The photonic band gap (PBG) of these TiO2 IO films was tuned by varying the sphere size of the PS CPC templates. The as-prepared N-F co-doped TiO2 IO films were used as photocatalysts for the degradation of Rhodamine B (RhB) dye under solar light irradiation. A significant enhancement in the photocatalytic activity was observed in N-F co-doped TiO2 IO films prepared using PS spheres of 215 nm as a template, with the red edge of the PBG closer to the electronic band gap (EBG) of TiO2. 100% of the dye molecules were degraded within 2 minutes under direct solar irradiation, which is one of the fastest reaction times ever reported for RhB degradation in the presence of TiO2 photocatalysts. The N-F co-doped TiO2 IO film prepared using PS of 460 nm with its PBG centered at 695 nm also showed good photocatalytic activity. It was found that the IO films displayed improved photocatalytic activity in comparison to ordinary nanocrystalline (nc)-TiO2 films. The enhancement could be attributed to the bandgap scattering effect and the slow photon effect, leading to a significant improvement in solar light harvesting.

  10. Enhanced photo catalytic performance of nickel doped bismuth selenide under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Kulsi, Chiranjit; Ghosh, Amrita; Mondal, Anup; Kargupta, Kajari; Ganguly, Saibal; Banerjee, Dipali

    2017-03-01

    We have reported photo catalytic properties of bismuth selenide (Bi2Se3) and nickel doped (5 mol%) bismuth selenide (Bi2Se3) samples on two different dyes, congo red (CR) and rose bengal (RB) under visible-light irradiation without and with hydrogen peroxide. A maximum rate constant of 0.0365 min-1 for RB dye has been observed for the nickel doped bismuth selenide catalyst in presence of hydrogen peroxide. A possible mechanism for improvement of photo catalytic performance has been explained based on band structure.

  11. Doping effects of vanadium pentoxide in hole injection layer for quantum dot light emitting diodes

    NASA Astrophysics Data System (ADS)

    Song, Suk-Ho; Song, Dae-Ho; Lee, Jun-Seo; Kim, Sang-Soo; Song, Jang-Kun

    2017-05-01

    We report the doping effect of V2O5 into hole injection layer (HIL) for quantum dot light emitting diodes (QD-LEDs). We used PEDOT:PSS for HIL, and by doping 0.1 wt% of V2O5 into PEDOT:PSS layer, the maximum external quantum efficiency was increased from 1 % to 1.28 % and the turn-on voltage was reduced from 14.65 V to 12.72 V, when compared to pure PEDOT:PSS. This indicates that V2O5 enhances the hole injection property for PEDOT:PSS layer.

  12. Visible light active photocatalytic degradation of bisphenol-A using nitrogen doped TiO2.

    PubMed

    Venkatachalam, N; Vinu, A; Anandan, S; Arabindoo, Banumathi; Murugesan, V

    2006-08-01

    Nitrogen doped titania was prepared by low temperature sol-gel method using titanium precursor and nitrogen containing bases like triethylamine and tetramethyl ammonium hydroxide compounds. The materials were characterized by XRD, BET, SEM, XPS, DRS-UV, and FT-IR techniques. DRS-UV study substantially indicates shift of the absorption edge of TiO2 to lower energy region. The phase composition, crystallinity, specific surface area, and visible light activity of nitrogen doped titania depend upon the preparation conditions. Photocatalytic degradation of bisphenol-A in aqueous medium was investigated by TiO2 and nitrogen doped TiO2 under visible light irradiation in a batch photocatalytic reactor. The results indicate higher visible light activity for nitrogen doped TiO2 than commercial TiO2 (Degussa P25) for bisphenol-A degradation. The influence of various parameters such as initial concentration of bisphenol-A, catalyst loading and pH was examined for maximum degradation efficiency.

  13. Synthesis of Mn-doped ZnS microspheres with enhanced visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Wang, Peng; Huang, Baibiao; Ma, Xiaojuan; Wang, Gang; Dai, Ying; Zhang, Xiaoyang; Qin, Xiaoyan

    2017-01-01

    ZnS microspheres with a series of Mn-doping concentration were synthesized via a facile solvothermal route. The phase structures, morphologies, and chemical states were characterized by X-ray powder diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The phase structure of the synthesized Mn-ZnS microspheres is hexagonal from the XRD patterns. UV-vis diffuse reflectance spectra were employed to analyze the absorption properties of the samples. The Mn-doped ZnS exhibited stronger visible light absorption with the increasing of Mn content. Their photocatalytic activities were evaluated by H2 production from water and reducing Cr6+ under visible light irradiation. The as-prepared Mn-doped ZnS exhibited better photocatalytic performance than that of pure ZnS and the optimal doping concentration was 7%. The enhancement in photocatalytic activity can be attributed to the expansion of light absorption and the increase in life time of photogenerated carriers.

  14. Radiation-induced gain degradation in lateral PNP BJTs with lightly and heavily doped emitters

    SciTech Connect

    Wu, A.; Schrimpf, R.D.; Pease, R.L.; Fleetwood, D.M.; Kosier, S.L.

    1997-06-01

    Ionizing radiation may cause failures in ICs due to gain degradation of individual devices. The base current of irradiated bipolar devices increases with total dose, while the collector current remains relatively constant. This results in a decrease in the current gain. Lateral PNP (LPNP) transistors typically exhibit more degradation than vertical PNP devices at the same total dose, and have been blamed as the cause of early IC failures at low dose rates. It is important to understand the differences in total-dose response between devices with heavily- and lightly-doped emitters in order to compare different technologies and evaluate the applicability of proposed low-dose-rate hardness-assurance methods. This paper addresses these differences by comparing two different LPNP devices from the same process: one with a heavily-doped emitter and one with a lightly-doped emitter. Experimental results demonstrate that the lightly-doped devices are more sensitive to ionizing radiation and simulations illustrate that increased recombination on the emitter side of the junction is responsible for the higher sensitivity.

  15. White light emission from GaN stack layers doped by different rare-earth metals

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Liu, Chang

    2015-02-01

    Experimental progress of electroluminescence devices (ELDs) employing GaN doped with rare-earth metals had been significantly made targeting RGB displays. However, reports on the theoretical models to design the devices and the applications were limited. Our previous paper proposed a device model using the quantum collision theory and Judd-Ofelt approximation to design the ELDs for white light illumination. In the present study, the model is modified by considering the light extraction efficiency and optical loss during propagating in the films. To improve the luminous efficiency, an ELD with three stack layers of GaN:Tm/GaN:Er/GaN:Eu is proposed and designed. The model predicts that the color of the integrated light can be controlled by applied voltage, thickness of each doping layer and doping concentrations of the rare earth metals. The luminous efficacy of white light emission at a bias of -100 V is calculated to be 274 lm/W, which is much higher than that of fluorescent lumps. The proposed ELD will open a door to efficient solid-state lighting.

  16. Wavelength-Tunable Electroluminescent Light Sources from Individual Ga-Doped ZnO Microwires.

    PubMed

    Jiang, Mingming; He, Gaohang; Chen, Hongyu; Zhang, Zhenzhong; Zheng, Lingxia; Shan, Chongxin; Shen, Dezhen; Fang, Xiaosheng

    2017-03-07

    Electrically driven wavelength-tunable light emission from biased individual Ga-doped ZnO microwires (ZnO:Ga MWs) is demonstrated. Single crystalline ZnO:Ga MWs with different Ga-doping concentrations have been synthesized using a one-step chemical vapor deposition method. Strong electrically driven light emission from individual ZnO:Ga MW based devices is realized with tunable colors, and the emission region is localized toward the center of the wires. Increasing Ga-doping concentration in the MWs can lead to the redshift of electroluminescent emissions in the visible range. Interestingly, owing to the lack of rectification characteristics, relevant electrical measurement results show that the alternating current-driven light emission functions excellently on the ZnO:Ga MWs. Consequently, individual ZnO:Ga MWs, which can be analogous to incandescent sources, offer unique possibilities for future electroluminescence light sources. This typical multicolor emitter can be used to rival and complement other conventional semiconductor devices in displays and lighting.

  17. White Light Emission Through Downconversion of Terbium and Europium Doped CeF3 Nanophosphors.

    PubMed

    Varun, S; Kalra, Mohit; Gandhi, Mayuri

    2015-09-01

    CeF3 nanophosphors have been extensively investigated in recent years for lighting and numerous bio-applications. Downconversion emissions in CeF3:Eu(3+)/Tb(3+) phosphors were studied with the objective of attaining a white light emitting composition, by means of a simple co-precipitation method. The material was characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Photoluminescence (PL). Uniformly distributed nanoparticles were obtained with an average particle size range of 8-10 nm. Various studies were undertook utilizing different doping concentrations and respective fluorescence studies were carried out to optimize dopant concentrations while achieving maximum luminescence intensity. From PL results, it was observed that the efficient energy transfers from the donor to the acceptor ions. Different concentrations of Tb(3+), Eu(3+) were doped in order to achieve a white light emitting phosphor for UV-based Light Emitting Diodes (LEDs). The nanoparticles showed characteristic emission of respective dopants (Eu(3+), Tb(3+)) when excited at the 4f → 5d transition of Ce(3+). The chromaticity coordinates for CeF3 doped with Eu(3+) and Tb(3+) were calculated and an emission very close to white light was observed.

  18. White light emission from Tm 3+/Dy 3+ co-doped oxyfluoride germanate glasses under UV light excitation

    NASA Astrophysics Data System (ADS)

    Lakshminarayana, G.; Yang, Hucheng; Qiu, Jianrong

    2009-04-01

    In this paper, we report on the absorption and photoluminescence properties of Tm 3+/Dy 3+ ions co-doped oxyfluoride germanate glasses for white light emission. The X-ray diffraction (XRD) and differential thermal analysis (DTA) profiles of the host glass have been carried out to confirm its structure and thermal stability. From the measured absorption spectra, Judd-Ofelt (J-O) intensity parameters ( Ω2, Ω4 and Ω6) have been evaluated for Tm 3+ and Dy 3+ ions. A combination of blue, yellow and red emissions has emerged in these glasses, which allows the observation of bright white light when the glasses are excited by the ultraviolet light. The white light luminescence colour could be changed by varying the excitation wavelength. Also, various colours of luminescence, including white light, can be easily tuned by adjusting the concentrations of Tm 3+ or Dy 3+ ions in the co-doped glasses. Concentration quenching effect was also investigated and possible energy transfer mechanism from Dy 3+→Tm 3+ ions was explained which is also confirmed by the decay lifetime measurements.

  19. Light-controlled electric Freedericksz threshold in dye doped liquid crystals

    SciTech Connect

    Lucchetti, L.; Catani, L.; Simoni, F.

    2014-05-28

    We report the results of measurements of the threshold of Freedericksz transition in a nematic liquid crystal doped by Methyl-red. We show that in case of dc field the threshold voltage can decrease or increase depending on the light dose, due to the light-induced desorption and adsorption of charge complexes from and on the irradiated surface, that has been recently demonstrated. This effect has the potential to be exploited in optical devices such as liquid crystal microlenses and spatial light modulators.

  20. Light controlled drug delivery containers based on spiropyran doped liquid crystal micro spheres

    PubMed Central

    Petriashvili, Gia; Devadze, Lali; Zurabishvili, Tsisana; Sepashvili, Nino; Chubinidze, Ketevan

    2016-01-01

    We have developed a novel, light activated drug delivery containers, based on spiropyran doped liquid crystal micro spheres. Upon exposure to UV/violet light, the spiropyran molecules entrapped inside the nematic liquid crystal micro spheres, interconvert from the hydrophobic, oil soluble form, to the hydrophilic, water soluble merocyanine one, which stimulates the translocation of the merocyanine molecules across the nematic liquid crystal-water barrier and results their homogeneous distribution throughout in an aqueous environment. Light controllable switching property and extremely high solubility of spiropyran in the nematic liquid crystal, promise to elaborate a novel and reliable vehicles for the drug delivery systems. PMID:26977353

  1. Strong blue light emission from Eu-doped SiOC prepared by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Lin, Zhenxu; Guo, Yanqing; Wang, Xiang; Song, Chao; Song, Jie; Zhang, Yi; Huang, Rui

    2015-08-01

    The Eu-doped SiOC films were prepared by magnetron sputtering technique at a low temperature of 250°C. The effects of the Eu2O3 deposited power and post-thermal annealing temperature on the PL characteristics of the Eu-doped SiOC films were investigated. It is found that the photoluminescence intensity could be enhanced by more than tenfold by increasing the Eu2O3 deposited power from 20W to 80W. Furthermore, very bright blue light emission can be clearly observed with the naked eye in a bright room for the Eu-doped SiOC films prepared at a Eu2O3 deposited power of 80 W. The improved PL intensity is attributed to the increasing number density of europium silicate clusters as a result of the increasing Eu2O3 deposited power as well as high annealing temperatures.

  2. Visible light-driven photocatalysis of doped SrTiO3 tubular structure.

    PubMed

    Shi, Jinwen; Shen, Shaohua; Chen, Yubin; Guo, Liejin; Mao, Samuel S

    2012-03-12

    SrTiO3 tubular structures co-doped with Cr and Ta were synthesized through a combination of solvothermal-hydrothermal processes. X-ray photoelectron spectroscopy (XPS) measurements of the oxidation state of Cr ions reveal that the formation of Cr6+ ions, which would serve as the non-radiative recombination centers for photogenerated electrons and holes, was suppressed without the process of high temperature hydrogen reduction. Compared to similar co-doped materials synthesized by solid-state reaction, (Cr, Ta) co-doped SrTiO3 tubular structures have significantly higher photocatalytic activity for hydrogen evolution as measured in an aqueous methanol solution under visible light irradiation.

  3. Improved photovoltaic performance of multiple carbon-doped ZnO nanostructures under UV and visible light irradiation.

    PubMed

    Liu, Xianbin; Du, Hejun; Sun, Xiao Wei; Zhan, Zhaoyao; Sun, Gengzhi; Li, Fengji; Zheng, Lianxi; Zhang, Sam

    2014-09-01

    We report synthesis of multiple carbon-doped ZnO nanostructures by using carbon cloth as substrates to obtain multiple hollow ZnO microtube-nanowire structures. X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy analysis clearly show that carbon is doped into ZnO through substitution of carbon for oxygen in the growth and annealing processes. Upon exposure to 633-nm red laser, a distinct photoresponse can be observed, which indicates that carbon doping in ZnO can well extend its light harvesting to visible light region. Furthermore, a prototype of photovoltaic cell was fabricated to demonstrate the photovoltaic performance of multiple carbon-doped ZnO nanostructures under UV and visible light irradiation. This result shows that carbon-doped ZnO can act as effective photoactive materials for photoelectric components.

  4. A hydrothermal synthesis of Pr3+ doped mesoporous TiO2 for UV light photocatalysis.

    PubMed

    Wang, Yong; Chen, Guihua; Shen, Qianhong; Yang, Hui; Li, Liquan; Song, Yanjiang

    2014-07-01

    Pr3+ doped mesoporous TiO2 photocatalysts with a different molar ratio of Pr to Ti were prepared by a hydrothermal method using triblock copolymer as the template. The as-prepared samples were systematically characterized by X-ray diffraction, N2 adsorption-desorption, X-ray photoelectron spectra, transmission electron microscopy and UV-visible diffuse reflectance spectroscopy. The characterizations indicated all the samples had mesoporous structure and narrow pore size distribution. Pr3+ doping enlarged the surface area and decreased the crystallite size. The surface area of the samples varied from 136 to 170 m2/g, and the average crystallite size ranged between 5.04 and 7.60 nm. The effect of Pr3+ doping amount on the photocatalytic activity of mesoporous TiO2 was evaluated by the degradation of methyl orange under UV light irradiation. The results showed that the suitable amount of Pr3+ doped samples exhibited the higher photocatalytic activity than mesoporous TiO2. Among the samples, 1 at.% Pr3+ doped mesoporous TiO2 showed the highest photocatalytic activity.

  5. N-type control of single-crystal diamond films by ultra-lightly phosphorus doping

    NASA Astrophysics Data System (ADS)

    Kato, Hiromitsu; Ogura, Masahiko; Makino, Toshiharu; Takeuchi, Daisuke; Yamasaki, Satoshi

    2016-10-01

    A wide impurity doping range of p- and n-type diamond semiconductors will facilitate the development of various electronics. This study focused on producing n-type diamond with ultra-lightly impurity doping concentrations. N-type single-crystal diamond films were grown on (111)-oriented diamond substrates by phosphorus doping using the optimized doping conditions based on microwave plasma-enhanced chemical vapor deposition with a high magnetron output power of 3600 W. The surface morphology was investigated by an optical microscopy using the Nomarski prism and confocal laser microscopy, and the phosphorus concentration was estimated by a secondary ion mass spectrometry. The phosphorus concentration was reproducibly controlled to between 2 × 1015 and 3 × 1017 cm-3 using a standard mass flow controller, and the average incorporation efficiency was around 0.1%. The electrical properties of the films were characterized by the Hall effect measurements as a function of temperature over a wide range from 220 to 900 K. N-type conductivity with thermal activation from a phosphorus donor level at around 0.57 eV was clearly observed for all the phosphorus-doped diamond films. The electron mobility of the film with a phosphorus concentration of 2 × 1015 cm-3 was recorded at 1060 cm2/V s at 300 K and 1500 cm2/V s at 225 K.

  6. Atomic-Layer-Confined Doping for Atomic-Level Insights into Visible-Light Water Splitting.

    PubMed

    Lei, Fengcai; Zhang, Lei; Sun, Yongfu; Liang, Liang; Liu, Katong; Xu, Jiaqi; Zhang, Qun; Pan, Bicai; Luo, Yi; Xie, Yi

    2015-08-03

    A model of doping confined in atomic layers is proposed for atomic-level insights into the effect of doping on photocatalysis. Co doping confined in three atomic layers of In2S3 was implemented with a lamellar hybrid intermediate strategy. Density functional calculations reveal that the introduction of Co ions brings about several new energy levels and increased density of states at the conduction band minimum, leading to sharply increased visible-light absorption and three times higher carrier concentration. Ultrafast transient absorption spectroscopy reveals that the electron transfer time of about 1.6 ps from the valence band to newly formed localized states is due to Co doping. The 25-fold increase in average recovery lifetime is believed to be responsible for the increased of electron-hole separation. The synthesized Co-doped In2S3 (three atomic layers) yield a photocurrent of 1.17 mA cm(-2) at 1.5 V vs. RHE, nearly 10 and 17 times higher than that of the perfect In2S3 (three atomic layers) and the bulk counterpart, respectively.

  7. Deep-ultraviolet-light-driven reversible doping of WS2 field-effect transistors.

    PubMed

    Iqbal, Muhammad Waqas; Iqbal, Muhammad Zahir; Khan, Muhammad Farooq; Shehzad, Muhammad Arslan; Seo, Yongho; Eom, Jonghwa

    2015-01-14

    Improvement of the electrical and photoelectric characteristics is essential to achieve an advanced performance of field-effect transistors and optoelectronic devices. Here we have developed a doping technique to drastically improve electrical and photoelectric characteristics of single-layered, bi-layered and multi-layered WS2 field-effect transistors (FET). After illuminating with deep ultraviolet (DUV) light in a nitrogen environment, WS2 FET shows an enhanced charge carrier density, mobility and photocurrent response. The threshold voltage of WS2 FET shifted toward the negative gate voltage, and the positions of E and A1g peaks in Raman spectra shifted toward lower wavenumbers, indicating the n-type doping effect of the WS2 FET. The doping effect is reversible. The pristine characteristics of WS2 FET can be restored by DUV light illumination in an oxygen environment. The DUV-driven doping technique in a gas environment provides a very stable, effective, easily applicable way to enhance the performance of WS2 FET.

  8. Light-induced rotation of dye-doped liquid crystal droplets.

    PubMed

    Manzo, C; Paparo, D; Marrucci, L; Jánossy, I

    2006-05-01

    We investigate both theoretically and experimentally the rotational dynamics of micrometric droplets of dye-doped and pure liquid crystal induced by circularly and elliptically polarized laser light. The droplets are dispersed in water and trapped in the focus of the laser beam. Since the optical torque acting on the molecular director is known to be strongly enhanced in light-absorbing dye-doped materials, the question arises whether a similar enhancement takes place also for the overall optical torque acting on the whole droplets. We searched for such enhancement by measuring and comparing the rotation speed of dye-doped droplets induced by a laser beam having a wavelength either inside or outside the dye absorption band, and also comparing it with the rotation of pure liquid crystal droplets. No enhancement was found, confirming that photoinduced dye effects are only associated with an internal exchange of angular momentum between orientational and translational degrees of freedom of matter. Our result provides also direct experimental proof of the existence of a photoinduced stress tensor in the illuminated dye-doped liquid crystal. Finally, peculiar photoinduced dynamical effects are predicted to occur in droplets in which the molecular director is not rigidly locked to the flow, but so far they could not be observed.

  9. Enhanced visible light photocatalytic activity of Gd-doped BiFeO3 nanoparticles and mechanism insight

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Chen, Da; Niu, Feng; Wang, Sen; Qin, Laishun; Huang, Yuexiang

    2016-05-01

    To investigate the effect of Gd doping on photocatalytic activity of BiFeO3 (BFO), Gd-doped BFO nanoparticles containing different Gd doping contents (Bi(1‑x)GdxFeO3, x = 0.00, 0.01, 0.03, 0.05) were synthesized using a facile sol-gel route. The obtained products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra, and ultraviolet-visible diffuse reflectance spectroscopy, and their photocatalytic activities were evaluated by photocatalytic decomposition of Rhodamine B in aqueous solution under visible light irradiation. It was found that the Gd doping content could significantly affect the photocatalytic activity of as-prepared Gd-doped BFO, and the photocatalytic activity increased with increasing the Gd doping content up to the optimal value and then decreased with further enhancing Gd doping content. To elucidate the enhanced photocatalytic mechanism of Gd-doped BFO, the trapping experiments, photoluminescence, photocurrent and electrochemical impedance measurements were performed. On the basis of these experimental results, the enhanced photocatalytic activities of Gd-doped BFO could be ascribed to the increased optical absorption, the efficient separation and migration of photogenerated charge carriers as well as the decreased recombination probability of electron-hole pairs derived from the Gd doping effect. Meanwhile, the possible photocatalytic mechanism of Gd-doped BFO was critically discussed.

  10. Enhanced visible light photocatalytic activity of Gd-doped BiFeO3 nanoparticles and mechanism insight

    PubMed Central

    Zhang, Ning; Chen, Da; Niu, Feng; Wang, Sen; Qin, Laishun; Huang, Yuexiang

    2016-01-01

    To investigate the effect of Gd doping on photocatalytic activity of BiFeO3 (BFO), Gd-doped BFO nanoparticles containing different Gd doping contents (Bi(1−x)GdxFeO3, x = 0.00, 0.01, 0.03, 0.05) were synthesized using a facile sol-gel route. The obtained products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra, and ultraviolet-visible diffuse reflectance spectroscopy, and their photocatalytic activities were evaluated by photocatalytic decomposition of Rhodamine B in aqueous solution under visible light irradiation. It was found that the Gd doping content could significantly affect the photocatalytic activity of as-prepared Gd-doped BFO, and the photocatalytic activity increased with increasing the Gd doping content up to the optimal value and then decreased with further enhancing Gd doping content. To elucidate the enhanced photocatalytic mechanism of Gd-doped BFO, the trapping experiments, photoluminescence, photocurrent and electrochemical impedance measurements were performed. On the basis of these experimental results, the enhanced photocatalytic activities of Gd-doped BFO could be ascribed to the increased optical absorption, the efficient separation and migration of photogenerated charge carriers as well as the decreased recombination probability of electron-hole pairs derived from the Gd doping effect. Meanwhile, the possible photocatalytic mechanism of Gd-doped BFO was critically discussed. PMID:27198166

  11. Dielectric study of azo-doped aerosil/7CB nematic nanocomposite upon UV light

    NASA Astrophysics Data System (ADS)

    Marinov, Y. G.; Marinov, M. P.; Hadjichristov, G. B.; Petrov, A. G.; Prasad, S. K.; Marino, L.; Scaramuzza, N.

    2017-01-01

    We studied three-component nanocomposite produced from nano-filled nematic by doping with photoactive azobenzene liquid crystal 4-(4‧-ethoxyphenylazo)phenyl hexanoate (EPH) at concentration of 3 wt.%. The photo-insensitive host nanocomposite material (the filled nematic) was a gel formed from the nematic 4-n-heptyl cyanobiphenyl (7CB) and 3 wt.% of silica nanospheres (hydrophilic Aerosil 300) of size ca. 7 nm. The electrochemical impedance spectroscopy was applied to determine the UV-light-produced effect in EPH-doped aerosil/7CB upon continuous trans-to-cis photoisomerization of EPH molecules by varying the UV light intensity. The effect from UV illumination on the dielectric permittivity function of the studied photoresponsive nematic nanocomposite was analyzed at a room temperature in the frequency range 0.5 Hz – 200 kHz.

  12. Spin Freezing and Recovery of Sublattice Magnetization in Lightly Doped Lanthanum Cuprate

    SciTech Connect

    Suh, B.J.; Hammel, P.C.; Sarrao, J.L.; Thompson, J.D.; Fisk, Z.; Hucker, M.; Buchner, B.

    1998-10-24

    {sup 139}La NQR studies in lightly doped La{sub 2}Cu{sub 1-x}Li{sub x}O{sub 4} and La{sub 1.8-x}Eu{sub 0.2}Sr{sub x}CuO{sub 4} are reviewed. A strong enhancement of the {sup 139}La relaxation rate with a peak accompanied by a sudden increase of the local field at low T has been observed similarly to La{sub 2-x}Sr{sub x}CuO{sub 4}. The anomalous magnetic properties are discussed in the light of the microscopic segregation of doped holes into hole-rich domain walls separating undoped AF domains.

  13. Physical and Electrical Characterization of 120 nm Technology Node Devices using PULSION registered Plasma Doping

    SciTech Connect

    Spiegel, Y.; Torregrosa, F.; Etienne, H.; Felch, S. B.; Roux, L.; Roux, P.; Figarols, F.; Grosjean, C.; Poupinet, S.; Regnier, P.; Delalleau, J.; Maillot, P.; Pizzuto, O.

    2011-01-07

    Plasma doping is a well-known technology used in semiconductor manufacturing for two major DRAM manufacturing steps: polysilicon counter-doping and contact doping. For these specific applications, the PULSION tool shows physical benefits, as well as cost of ownership benefits, with the capability to perform low energy, high dose implantation in a high throughput mode. Nevertheless, throughput is a common challenge for all semiconductor manufacturing, not only for advanced technologies. The purpose of this study is to demonstrate that plasma doping is not limited to advanced devices, but can also satisfy the requirements of >90 nm nodes, for specific applications such as Lightly Doped Drain (LDD) implants.

  14. Blue-green variable light-emitting diode based on organic-molecule-doped polymer

    NASA Astrophysics Data System (ADS)

    Xu, Chunxiang; Cui, Yiping; Shen, Yingzhong; Gu, Hongwei; Pan, Yi; Li, Yinkui

    1999-09-01

    Monolayer organic light-emitting diodes based on the organic molecule [(3,4-dimethoxybenzyldehycle-2'-hydroxy naphthylimine)dimethyl gallium]-doped [poly(2-mehtyoxy-5-ethyloxy)-4-di-(2-methyoxy-5'-octaoxy)phenylene vinylene] have been fabricated by a spin-coating method. Color variation from green to blue has been observed. The results have been attributed to the variation of the recombination zone and the charge transfer between the materials.

  15. Highly Active TiO2-Based Visible-Light Photocatalyst with Nonmetal Doping and Plasmonic Metal Decoration

    SciTech Connect

    Zhang, Qiao; Lima, Diana Q.; Chi, Miaofang; Yin, Yadong

    2011-01-01

    A sandwich-structured photocatalyst shows an excellent performance in degradation reactions of a number of organic compounds under UV, visible light, and direct sunlight (see picture). The catalyst was synthesized by a combination of nonmetal doping and plasmonic metal decoration of TiO2 nanocrystals, which improves visible-light activity and enhances light harvesting and charge separation, respectively.

  16. Electrical conduction mechanism in annealed and light soaked silver doped CdSe thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdish; Tripathi, S. K.

    2015-08-01

    Thin films of silver (Ag) doped CdSe are prepared on glass substrates by thermal evaporation technique in inert gas atmosphere. SEM micrograph reveals uniform and homogenous distribution of nanoparticles on the glass substrates. The composition of the film is investigated by EDX analysis. Thin films are thermally annealed and light soaked to study the thermally and optically induced effect. Electrical conduction in annealed thin films exhibits different conduction mechanisms in low and high temperature region while conduction in light soaked thin films is single thermally activated process. The activation energies for dark and photoconductivities are also investigated.

  17. Facile synthesis of cobalt-doped zinc oxide thin films for highly efficient visible light photocatalysts

    NASA Astrophysics Data System (ADS)

    Altintas Yildirim, Ozlem; Arslan, Hanife; Sönmezoğlu, Savaş

    2016-12-01

    Cobalt-doped zinc oxide (Co:ZnO) thin films with dopant contents ranging from 0 to 5 at.% were prepared using the sol-gel method, and their structural, morphological, optical, and photocatalytic properties were characterized. The effect of the dopant content on the photocatalytic properties of the films was investigated by examining the degradation behavior of methylene blue (MB) under visible light irradiation, and a detailed investigation of their photocatalytic activities was performed by determining the apparent quantum yields (AQYs). Co2+ ions were observed to be substitutionally incorporated into Zn2+ sites in the ZnO crystal, leading to lattice parameter constriction and band gap narrowing due to the photoinduced carriers produced under the visible light irradiation. Thus, the light absorption range of the Co:ZnO films was improved compared with that of the undoped ZnO film, and the Co:ZnO films exhibited highly efficient photocatalytic activity (∼92% decomposition of MB after 60-min visible light irradiation for the 3 at.% Co:ZnO film). The AQYs of the Co:ZnO films were greatly enhanced under visible light irradiation compared with that of the undoped ZnO thin film, demonstrating the effect of the Co doping level on the photocatalytic activity of the films.

  18. Photonic crystal light emitting diode based on Er and Si nanoclusters co-doped slot waveguide

    SciTech Connect

    Lo Savio, R.; Galli, M.; Liscidini, M.; Andreani, L. C.; Franzò, G.; Iacona, F.; Miritello, M.; Irrera, A.; Sanfilippo, D.; Piana, A.; Priolo, F.

    2014-03-24

    We report on the design, fabrication, and electro-optical characterization of a light emitting device operating at 1.54 μm, whose active layer consists of silicon oxide containing Er-doped Si nanoclusters. A photonic crystal (PhC) is fabricated on the top-electrode to enhance the light extraction in the vertical direction, and thus the external efficiency of the device. This occurs if a photonic mode of the PhC slab is resonant with the Er emission energy, as confirmed by theoretical calculations and experimental analyses. We measure an increase of the extraction efficiency by a factor of 3 with a high directionality of light emission in a narrow vertical cone. External quantum efficiency and power efficiency are among the highest reported for this kind of material. These results are important for the realization of CMOS-compatible efficient light emitters at telecom wavelengths.

  19. Sb-doped p-type ZnO and its application on light emitting devices

    NASA Astrophysics Data System (ADS)

    Chu, Sheng; Leela, Leelaprasanna J.; Yang, Zheng; Lim, Jae Hong; Li, Lin; Liu, Jianlin

    2008-03-01

    Reliable Sb-doped p-type ZnO on silicon substrate was grown by molecular beam epitaxy. The hole concentrations up to 10^19/cm^3 were achieved by tuning the Sb cell temperature. The results from XPS and photoluminescence spectrum confirmed the theoretical prediction that the Sb doping mechanism in ZnO is the formation of complex shallow acceptor SbZn+2VZn, with a low ionization energy of about 150meV. Then ZnO p-n homojunction light emitting diodes (LED) were fabricated based on the p-type Sb-doped layer, and the Ga-doped n-type ZnO layer. Low specific resistivity Au/NiO and Au/Ti contacts were deposited on top of the p-type and n-type layers, respectively, and the contacts were annealed to obtain ohmic conduction. Electroluminescence measurements were performed on the devices under different temperatures and injection currents. Strong near-band edge emissions were clearly observed at room and low temperatures. The device exhibited dominant UV peak at 3.31eV over the deep level emissions at 9K, which is the result from the large build in potential in the junction and the good film quality.

  20. Photocatalytic performance of Fe-doped TiO2 nanoparticles under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Ali, T.; Tripathi, P.; Azam, Ameer; Raza, Waseem; Ahmed, Arham S.; Ahmed, Ateeq; Muneer, M.

    2017-01-01

    The present work focuses on the synthesis, characterization and photocatalytic activity of a nanosized Fe-doped TiO2 photocatalyst. The samples were synthesized by the sol–gel method and characterized by using techniques such as x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), UV–visible spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy and Fourier-transform infrared (FTIR). The powder XRD spectra revealed that the synthesized samples are pure and crystalline in nature and show a tetragonal anatase phase of TiO2. The Raman spectroscopy also confirmed the formation of an anatase phase structure in both pure and Fe-doped TiO2 nanoparticles (NPs). The UV–visible and PL spectra illustrated the red shift in Fe-doped TiO2 NPs. The FTIR spectra indicated the vibrational band of the Ti–O lattice. The photocatalytic experimental results demonstrate that Fe-doped TiO2 NPs effectively degrade MB under visible-light illumination. Interestingly, the prepared TiO2 NPs with a dopant concentration of 3.0 mole% showed the maximum photocatalytic activity under investigation.

  1. Improved efficiency in blue phosphorescent organic light-emitting diodes by the stepwise doping structure

    NASA Astrophysics Data System (ADS)

    Yang, Liping; Wang, Xiaoping; Kou, Zhiqi; Ji, Changyan

    2017-04-01

    The electro-optical properties of the blue phosphorescent organic light-emitting diodes (PHOLEDs) can be affected by the stepwise doping structure in the emitting layer (EML). A series of multi-EML devices with different doping concentration of blue dopant (FIrpic) are fabricated. The effect of the stepwise doping structure close to the electron transport layer is more obvious than that close to the hole transport layer. When the doping concentration increases gradually from the hole injection side to the electron injection side, the maximum values of the luminance, current and power efficiency can reach to 9745 cd/m2 (at 9 V), 32.0 cd/A and 25.1 lm/W in the device with the asymmetric tri-EML structure, which is improved by about 10% compared with that in the bi-EML device. When the number of the EML is four, the performance of the device becomes worse because of the interface effect resulting from different concentration of dopant.

  2. Hydrogenated aluminium-doped zinc oxide semiconductor thin films for polymeric light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Hao, X. T.; Zhu, F. R.; Ong, K. S.; Tan, L. W.

    2006-01-01

    Highly conducting transparent thin films of aluminium(Al)-doped zinc oxide (ZnO:Al) were deposited by a radio frequency magnetron-sputtering technique using an argon and hydrogen gas mixture at room temperature. Hydrogen serves as a shallow donor and plays a critical role in improving the Al doping efficiency to enhance the conductivity of thin films. The effect of hydrogen partial pressure on the properties of ZnO:Al films was investigated in detail. Polycrystalline ZnO:Al films with a surface roughness of about 2 nm, conductivity of 1.97 × 103 S cm-1, transmittance of over 83% in the visible wavelength region and an optical band gap of 3.93 eV were achieved at a hydrogen partial pressure of 7.5 × 10-4 Pa. A ZnO:Al film with the desired properties was used as an anode contact in a bi-layer polymeric light-emitting diode. A polyethylene dioxythiophene-polystyrene sulfonate doped with poly(styrenesulfonic acid) (PEDOT: PSS) and phenyl-substituted poly(p-phenylene vinylene) (Ph-PPV) were employed as a hole transport layer and a light-emitting layer, respectively. The electro-luminescence performance of the aforementioned diode was studied and compared to a control device with an indium tin oxide anode.

  3. Visible light carrier generation in co-doped epitaxial titanate films

    SciTech Connect

    Comes, Ryan B.; Smolin, Sergey Y.; Kaspar, Tiffany C.; Gao, Ran; Apgar, Brent A.; Martin, Lane W.; Bowden, Mark E.; Baxter, Jason; Chambers, Scott A.

    2015-03-02

    Perovskite titanates such as SrTiO3 (STO) exhibit a wide range of important functional properties, including high electron mobility, ferroelectricity—which may be valuable in photovoltaic applications—and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications, however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr3+ dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to between 2.4 and 2.7 eV depending on doping levels. Transient reflectance measurements confirm that optically generated carriers have a recombination lifetime comparable to that of STO and are in agreement with the observations from ellipsometry. Finally, through photoelectrochemical yield measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  4. Antibacterial and Photodegradative Properties of Metal Doped TiO2 thin Films Under Visible Light.

    PubMed

    Ogorevc, Jerneja Šauta; Tratar-Pirc, Elizabeta; Matoh, Lev; Peter, Bukovec

    2012-06-01

    Doped (Au, Ag) and undoped TiO2 thin films were prepared on soda-lime glass via the sol-gel method by dip-coating from TiCl4 precursor, followed by 30 minutes calcination at 500 °C to obtain transparent thin films with good adhesion to the substrate. XRD analysis showed that the particle size of samples heat treated at 500 °C was ~10 nm for all of the samples prepared, both doped and undoped ones. SEM images revealed that the thin film surface was homogeneous and nano-porous. The hydrophilicity of the thin films was estimated by contact angle measurements. The photodegradation rate of an aqueous solution of the azo dye Plasmocorinth B on the thin films was tested by in-situ UV-Vis spectroscopic measurements of the dye solution. The best photocatalytic activity under visible and UVA light was exhibited by undoped TiO2 thin films, whereas Au doped thin films were slightly less active. On the other hand, the best antimicrobial activity toward the E. coli strain DH5a under visible light was displayed by the Au/TiO2 thin films.

  5. Microemulsion synthesis, characterization of highly visible light responsive rare earth-doped Bi2O3.

    PubMed

    Wu, Shuxing; Fang, Jianzhang; Xu, Xiaoxin; Liu, Zhang; Zhu, Ximiao; Xu, Weicheng

    2012-01-01

    In this paper, Bi(2)O(3) and rare earth (La, Ce)-doped Bi(2)O(3) visible-light-driven photocatalysts were prepared in a Triton X-100/n-hexanol/cyclohexane/water reverse microemulsion. The resulting materials were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area, photoluminescence spectra (PLS) and UV-Vis diffuse reflectance spectroscopy. The XRD patterns of the as-prepared catalysts calcined at 500 °C exhibited only the characteristic peaks of monoclinic α-Bi(2)O(3). PLS analysis implied that the separation efficiency for electron-hole has been enhanced when Bi(2)O(3) was doped with rare earth. UV-Vis diffuse reflectance spectroscopy measurements presented an extension of light absorption into the visible region. The photocatalytic activity of the samples was evaluated by degradation of methyl orange (MO) and 2,4-dichlorophenol (2,4-DCP). The results displayed that the photocatalytic activity of rare earth-doped Bi(2)O(3) was higher than that of dopant-free Bi(2)O(3). The optimal dopant amount of La or Ce was 1.0 mol%. And the mechanisms of influence on the photocatalytic activity of the catalysts were discussed.

  6. Preparation and visible light photocatalytic activity of N-doped titania.

    PubMed

    Hu, Yulong; Liu, Hongfang; Chen, Weiran; Chen, Debin; Yin, Jiwei; Guo, Xingpeng

    2010-03-01

    N-doped titania powders were prepared with titanium tetraisopropoxide (TTIP) as the titanium source and urea as the nitrogen source by the sol-gel method. The samples were characterized using X-ray diffraction (XRD), diffuse reflectance spectrum (DRS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The XRD and TEM results indicated that urea played an important role in controlling the size and aggregation process of titania nanoparticles. As an appropriate amount of urea was added into the titania sol, the size of the particles decreased. However, the excess urea reduced the dispersion of the particles and resulted in the aggregation. At the same time, the size of particle increased, and the size distribution broadened. The XPS and DRS results showed that the nitrogen was incorporated into titania lattice successfully, which brought about the redshift of the absorption edge and induced the photocatalytic activity in the visible light region. The photocatalytic experiments showed that the N-doped titania nanoparticles could effectively photodegrade methyl orange (MO) aqueous solution under visible light irradiation. The photocatalytic activity increased with the increase of the nitrogen doping level in the titania lattice, but decreased with the increase of the particle size and the organic surface residues caused by excess urea.

  7. Chromatic-stability white organic light emitting diodes based on phosphorescence doped electron transport layer

    NASA Astrophysics Data System (ADS)

    Zhou, Pengchao; Wang, Feifei; Lin, Hong; Li, Xifeng; Tong, Liang; Wei, Na; Gao, Zhixiang; Wei, Bin

    2014-04-01

    The influence of fac-tris(2-phenylpyridine)iridium [Ir(ppy)3] doped into electron transport layer was investigated by a series of electron-only devices, and the mechanism of the reduced field-dependent electron-transporting properties was also discussed. Utilizing the method of optimized doping concentration, a hybrid white organic light emitting diode with high efficiency, low efficiency roll-off and stable spectra was fabricated. Organic layer doped Ir(ppy)3 serves two functions: emit supernumerary green light with excess holes when the applied bias are low; weaken electron-transport ability when the bias increase. Both the two functions can improve the carrier balance and confine the exciton recombination region. For Device B, the maximum current efficiency and power efficiency reach 37.4 cd/A and 28.6 lm/W, respectively. The Commision Internationale de l’Éclairage (CIE) coordinates vary slightly from (0.48, 0.43) at 1.1 cd/m2 to (0.46, 0.43) at 18,600 cd/m2.

  8. Fluorescence properties and white light generation from Dy3+-doped niobium phosphate glasses

    NASA Astrophysics Data System (ADS)

    Srihari, T.; Jayasankar, C. K.

    2017-07-01

    Niobium phosphate glasses (P2O5+Nb2O5+K2O + Al2O3+Dy2O3) doped with different concentrations of Dy3+ ions have been synthesized by melt quenching technique and characterized through structural and optical measurements to evaluate the fluorescence properties and find their suitability for white light emitting diodes (LEDs). Phonon energy and vibrational groups of the host matrix have been analyzed from Raman spectra. Judd-Ofelt analysis has been applied for 1.0 mol% Dy2O3-doped glass and inturn radiative properties have been evaluated for excited states of the Dy3+ ion. The higher value of stimulated emission cross-section (σe = 6.4 × 10-21 cm2) for the 4F9/2 → 6H13/2 level confirms its potentiality to be used as yellow laser. The decay curves exhibit non-exponential nature at higher concentrations (≥1 mol %) of Dy3+ ion. From the decay curve analysis, the quantum efficiency for the 4F9/2 level of 1.0 mol % Dy3+-doped glass is found to be 92%. The yellow to blue intensity ratios and chromaticity color co-ordinates are found to vary with Dy3+ ion concentrations/excitation wavelengths and are within the white light region.

  9. Integrated oxygen-doping and dye sensitization of graphitic carbon nitride for enhanced visible light photodegradation.

    PubMed

    Liu, Shizhen; Sun, Hongqi; Ang, H M; Tade, Moses O; Wang, Shaobin

    2016-08-15

    Graphitic carbon nitride (GCN) is a promising metal-free photocatalyst while suffering from low charge mobility induced inefficient photocatalysis. In this work, oxygen doping was employed to enhance the photodegradation of organic pollutants in water on graphitic carbon nitride (GCNO) under visible light. For further absorption extension, four organic dyes (Eosin-Y, Perylene, Nile-red and Coumarin) were adopted to dye-sensitize the GCNO photocatalyst. It was found that O-doping can promote dye sensitization, which was dependent on the type of dyes and influenced the photodegradation efficiencies of methylene blue (MB) and phenol. Nile-red sensitized GCNO presented the best activity in MB degradation under λ>480nm irradiations while Eosin-Y showed the best sensitization performance for phenol degradation under λ>420nm light source. However, dye sensitization was not effective for enhanced pollutant degradation on GCN without O-doping. UV-vis diffuse reflectance spectra (UV-vis DRS), photoluminescence (PL) spectra, and photocurrent analyses were applied to investigate the mechanism of carriers' transfer, which indicated that dye molecules could inject extra electrons into GCNO energy band and the energy dislocation could suppress electron/hole recombination, enhancing photocatalytic performances.

  10. Visible light carrier generation in co-doped epitaxial titanate films

    SciTech Connect

    Comes, Ryan B. Kaspar, Tiffany C.; Chambers, Scott A.; Smolin, Sergey Y.; Baxter, Jason B.; Gao, Ran; Apgar, Brent A.; Martin, Lane W.; Bowden, Mark E.

    2015-03-02

    Perovskite titanates such as SrTiO{sub 3} (STO) exhibit a wide range of important functional properties, including ferroelectricity and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications; however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr, we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr{sup 3+} dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to 2.4–2.7 eV depending on doping levels. Transient reflectance spectroscopy measurements are in agreement with the observations from ellipsometry and confirm that optically generated carriers are present for longer than 2 ns. Finally, through photoelectrochemical methylene blue degradation measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  11. Enhanced Visible Light Photocatalytic Activity of ZnO Nanowires Doped with Mn2+ and Co2+ Ions

    PubMed Central

    Li, Wei; Wang, Guojing; Chen, Chienhua; Liao, Jiecui; Li, Zhengcao

    2017-01-01

    In this research, ZnO nanowires doped with Mn2+ and Co2+ ions were synthesized through a facile and inexpensive hydrothermal approach, in which Mn2+ and Co2+ ions successfully substituted Zn2+ in the ZnO crystal lattice without changing the morphology and crystalline structure of ZnO. The atomic percentages of Mn and Co were 6.29% and 1.68%, respectively, in the doped ZnO nanowires. The photocatalytic results showed that Mn-doped and Co-doped ZnO nanowires both exhibited higher photocatalytic activities than undoped ZnO nanowires. Among the doped ZnO nanowires, Co-doped ZnO, which owns a twice active visible-light photocatalytic performance compared to pure ZnO, is considered a more efficient photocatalyst material. The enhancement of its photocatalytic performance originates from the doped metal ions, which enhance the light absorption ability and inhibit the recombination of photo-generated electron-hole pairs as well. The effect of the doped ion types on the morphology, crystal lattice and other properties of ZnO was also investigated. PMID:28336854

  12. Visible Light-Driven Photocatalytic Performance of N-Doped ZnO/g-C3N4 Nanocomposites

    NASA Astrophysics Data System (ADS)

    Kong, Ji-Zhou; Zhai, Hai-Fa; Zhang, Wei; Wang, Shan-Shan; Zhao, Xi-Rui; Li, Min; Li, Hui; Li, Ai-Dong; Wu, Di

    2017-09-01

    N-doped ZnO/g-C3N4 composites have been successfully prepared via a facile and cost-effective sol-gel method. The nanocomposites were systematically characterized by XRD, FE-SEM, HRTEM, FT-IR, XPS, and UV-vis DRS. The results indicated that compared with the pure N-doped ZnO, the absorption edge of binary N-doped ZnO/g-C3N4 shifted to a lower energy with increasing the visible-light absorption and improving the charge separation efficiency, which would enhance its photocatalytic activity. Compared with the pure g-C3N4, ZnO, N-doped ZnO and the composite ZnO/g-C3N4, the as-prepared N-doped ZnO/g-C3N4 exhibits a greatly enhanced photocatalytic degradation of methylene blue and phenol under visible-light irradiation. Meanwhile, N-doped ZnO/g-C3N4 possesses a high stability. Finally, a proposed mechanism for N-doped ZnO/g-C3N4 is also discussed. The improved photocatalysis can be attributed to the synergistic effect between N-doped ZnO and g-C3N4, including the energy band structure and enhanced charge separation efficiency.

  13. A controllable growth-doping approach to synthesize bright white-light-emitting Cd:In2S3 nanocrystals

    NASA Astrophysics Data System (ADS)

    Feng, Jian; Zhu, Hui; Yang, Xiurong

    2013-06-01

    A new type of doped Cd:In2S3 NC, which exhibits bright white-light emission with a QY of about 18%, synthesized by a one-pot G-doping synthesis approach is presented. The successful realization of temporal separation of nucleation doping and growth doping makes this approach a facile method to synthesize the In2S3/Cd:In2S3 core/shell nanostructure.A new type of doped Cd:In2S3 NC, which exhibits bright white-light emission with a QY of about 18%, synthesized by a one-pot G-doping synthesis approach is presented. The successful realization of temporal separation of nucleation doping and growth doping makes this approach a facile method to synthesize the In2S3/Cd:In2S3 core/shell nanostructure. Electronic supplementary information (ESI) available: Detailed synthetic procedure, ICP-MS, TEM, HRTEM, PL decay curves, CIE coordinates and CCT of Cd:In2S3 NCs, and PL spectra of In2S3 and CdS. See DOI: 10.1039/c3nr00878a

  14. Enhanced Visible Light Photocatalytic Activity of ZnO Nanowires Doped with Mn(2+) and Co(2+) Ions.

    PubMed

    Li, Wei; Wang, Guojing; Chen, Chienhua; Liao, Jiecui; Li, Zhengcao

    2017-01-19

    In this research, ZnO nanowires doped with Mn(2+) and Co(2+) ions were synthesized through a facile and inexpensive hydrothermal approach, in which Mn(2+) and Co(2+) ions successfully substituted Zn(2+) in the ZnO crystal lattice without changing the morphology and crystalline structure of ZnO. The atomic percentages of Mn and Co were 6.29% and 1.68%, respectively, in the doped ZnO nanowires. The photocatalytic results showed that Mn-doped and Co-doped ZnO nanowires both exhibited higher photocatalytic activities than undoped ZnO nanowires. Among the doped ZnO nanowires, Co-doped ZnO, which owns a twice active visible-light photocatalytic performance compared to pure ZnO, is considered a more efficient photocatalyst material. The enhancement of its photocatalytic performance originates from the doped metal ions, which enhance the light absorption ability and inhibit the recombination of photo-generated electron-hole pairs as well. The effect of the doped ion types on the morphology, crystal lattice and other properties of ZnO was also investigated.

  15. Visible Light-Driven Photocatalytic Performance of N-Doped ZnO/g-C3N4 Nanocomposites.

    PubMed

    Kong, Ji-Zhou; Zhai, Hai-Fa; Zhang, Wei; Wang, Shan-Shan; Zhao, Xi-Rui; Li, Min; Li, Hui; Li, Ai-Dong; Wu, Di

    2017-09-06

    N-doped ZnO/g-C3N4 composites have been successfully prepared via a facile and cost-effective sol-gel method. The nanocomposites were systematically characterized by XRD, FE-SEM, HRTEM, FT-IR, XPS, and UV-vis DRS. The results indicated that compared with the pure N-doped ZnO, the absorption edge of binary N-doped ZnO/g-C3N4 shifted to a lower energy with increasing the visible-light absorption and improving the charge separation efficiency, which would enhance its photocatalytic activity. Compared with the pure g-C3N4, ZnO, N-doped ZnO and the composite ZnO/g-C3N4, the as-prepared N-doped ZnO/g-C3N4 exhibits a greatly enhanced photocatalytic degradation of methylene blue and phenol under visible-light irradiation. Meanwhile, N-doped ZnO/g-C3N4 possesses a high stability. Finally, a proposed mechanism for N-doped ZnO/g-C3N4 is also discussed. The improved photocatalysis can be attributed to the synergistic effect between N-doped ZnO and g-C3N4, including the energy band structure and enhanced charge separation efficiency.

  16. Nanoscale determination of the mass enhancement factor in the lightly doped bulk insulator lead selenide

    PubMed Central

    Zeljkovic, Ilija; Scipioni, Kane L.; Walkup, Daniel; Okada, Yoshinori; Zhou, Wenwen; Sankar, R; Chang, Guoqing; Wang, Yung Jui; Lin, Hsin; Bansil, Arun; Chou, Fangcheng; Wang, Ziqiang; Madhavan, Vidya

    2015-01-01

    Bismuth chalcogenides and lead telluride/selenide alloys exhibit exceptional thermoelectric properties that could be harnessed for power generation and device applications. Since phonons play a significant role in achieving these desired properties, quantifying the interaction between phonons and electrons, which is encoded in the Eliashberg function of a material, is of immense importance. However, its precise extraction has in part been limited due to the lack of local experimental probes. Here we construct a method to directly extract the Eliashberg function using Landau level spectroscopy, and demonstrate its applicability to lightly doped thermoelectric bulk insulator PbSe. In addition to its high energy resolution only limited by thermal broadening, this novel experimental method could be used to detect variations in mass enhancement factor at the nanoscale level. This opens up a new pathway for investigating the local effects of doping and strain on the mass enhancement factor. PMID:25814140

  17. Fabrication of polymer light-emitting diodes using doped silicon electrodes

    NASA Astrophysics Data System (ADS)

    Parker, I. D.; Kim, Helen H.

    1994-04-01

    The paper presents the manufacture of light emitting diodes on Si substrates using semiconducting electroluminescent polymers. The substrate which serves as an electrode material is a doped n and p Si. Device characteristics can be explained by a simple band-based model with little or no band bending, as a result of low doping levels. Electrons tunnel through a triangular barrier caused by the offset between the Fermi level of the cathode and the lowest unoccupied molecular orbital (LUMO) of the MEH-PPV. Holes tunnel through a similar barrier due to the offset between the anode and the highest occupied molecular orbital (HOMO). Electroluminescence occurs through the radiative recombination of charged polarons generated by self-localization of charge on the polymer chain. The forward and reverse bias characteristics for both n- and p- Si/MEH-PPV/Ca device is illustrated.

  18. Hybrid Structure White Organic Light Emitting Diode for Enhanced Efficiency by Varied Doping Rate.

    PubMed

    Kim, Dong-Eun; Kang, Min-Jae; Park, Gwang-Ryeol; Kim, Nam-Kyu; Lee, Burm-Jong; Kwon, Young-Soo; Shin, Hoon-Kyu

    2016-03-01

    Novel materials based on Zn(HPB)2 and Ir-complexes were synthesized as blue or red emitters, respectively. White organic light emitting diodes were fabricated using the Zn(HPB)2 as a blue emitting layer, Ir-complexes as a red emitting layer and Alq3 as a green emitting layer. The obtained experimental results, were based on white OLEDs fabricated using double emission layers of Zn(HPB)2 and Alq3:Ir-complexes. The doping rate of the Ir-complexes was varied at 0.4%, 0.6%, 0.8% and 1.0%. When the doping rate of the Alq3:Ir-complexes was 0.6%, a white emission was achieved. The Commission Internationale de l'Eclairage coordinates of the device's white emission were (0.316, 0.331) at an applied voltage of 10.75 V.

  19. Color tunable light-emitting diodes based on copper doped semiconducting nanocrystals

    NASA Astrophysics Data System (ADS)

    Bhaumik, Saikat; Ghosh, Batu; Pal, Amlan J.

    2011-08-01

    We have introduced copper-doped semiconducting nanocrystals in light-emitting diodes (LEDs). Characteristics of the devices show that electroluminescence (EL) emission in these LEDs is color tunable. In copper-doped ZnS nanocrystals in the core and Zn1-xCdxS host as a shell-layer, photoluminescence (PL) arises from a transition from conduction band-edge of the host to 3d-levels of copper-ions. The PL of the nanocrystals and hence the EL of LEDs based on such nanostructures become tunable by varying the Cd-content in Zn-Cd-S alloys, that is, Zn1-xCdxS with different values of x, which changes the conduction band-edge of the host.

  20. Structure and photoluminescence properties of nanocrystal Eu{sup 3+}-doped gadolinium tungsten red emitting phosphors excited by blue light

    SciTech Connect

    Shi, W.; He, H.; Zhang, X.; Feng, A.L.; Li, G.

    2012-11-15

    Highlights: ► We get a series of Eu{sup 3+} doped tungstate phosphors with a wide range doping level. ► Different doping level leads to different crystal structures of final productions. ► Gd{sub 6}WO{sub 12}-like with a tetragonal lattice structure grows at low doping level. ► Gd{sub 2}WO{sub 6}-like with a monoclinic lattice structure grows at high doping level. ► The doping level at 40 mol% Eu{sup 3+} excited by blue light shows excellent red emission. -- Abstract: A co-precipitation reaction was used to prepare nanocrystal Gd{sub 6}WO{sub 12}:Eu{sup 3+} and Gd{sub 2}WO{sub 6}:Eu{sup 3+} red emitting phosphor powders with different Eu{sup 3+} doping levels. It is found that under the same preparation conditions, different doping level leads to different crystal structures; Gd{sub 6}WO{sub 12}-like with a tetragonal lattice structure tends to be synthesized at low doping level (10–40 mol%) yet Gd{sub 2}WO{sub 6}-like with a monoclinic lattice structure easily to grow at high doping level (60–80 mol%). The strong red emission of {sup 5}D{sub 0} → {sup 7}F{sub 2} transitions at 620 nm was observed for all powders under either near ultraviolet or blue light excited and the most intense emission was obtained at the concentration of 40 mol%. This kind of powders might find their promising application to compensate the white LEDs for the lack of red light component and to improve rendering index.

  1. The Draining Cylinder

    ERIC Educational Resources Information Center

    James Graham-Eagle

    2009-01-01

    This article explores the time it takes for a liquid to drain from a cylindrical container through a hole in the bottom. Using dimensional analysis and some thought experiments this time is determined and Torricelli's law derived as a consequence. Finally, the effect of pouring liquid into the container as it drains is considered.

  2. The Draining Cylinder

    ERIC Educational Resources Information Center

    James Graham-Eagle

    2009-01-01

    This article explores the time it takes for a liquid to drain from a cylindrical container through a hole in the bottom. Using dimensional analysis and some thought experiments this time is determined and Torricelli's law derived as a consequence. Finally, the effect of pouring liquid into the container as it drains is considered.

  3. Characterization and improved solar light activity of vanadium doped TiO2/diatomite hybrid catalysts.

    PubMed

    Wang, Bin; Zhang, Guangxin; Leng, Xue; Sun, Zhiming; Zheng, Shuilin

    2015-03-21

    V-doped TiO2/diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol-gel method. The diatomite was responsible for the well dispersion of TiO2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO2/diatomite hybrids showed red shift in TiO2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO2 bandgap due to V(4+) ions substituted to Ti(4+) sites. The 0.5% V-TiO2/diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO2/diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V(4+) ions incorporated in TiO2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO2 to produce superoxide radicals ˙O2(-), while V(5+) species presented on the surface of TiO2 particles in the form of V2O5 contributed to e(-)-h(+) separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Enhanced photoluminescence of Si nanocrystals-doped cellulose nanofibers by plasmonic light scattering

    SciTech Connect

    Sugimoto, Hiroshi; Zhang, Ran; Reinhard, Björn M.; Fujii, Minoru; Perotto, Giovanni; Marelli, Benedetto; Omenetto, Fiorenzo G.; Dal Negro, Luca

    2015-07-27

    We report the development of bio-compatible cellulose nanofibers doped with light emitting silicon nanocrystals and Au nanoparticles via facile electrospinning. By performing photoluminescence (PL) spectroscopy as a function of excitation wavelength, we demonstrate plasmon-enhanced PL by a factor of 2.2 with negligible non-radiative quenching due to plasmon-enhanced scattering of excitation light from Au nanoparticles to silicon nanocrystals inside the nanofibers. These findings provide an alternative approach for the development of plasmon-enhanced active systems integrated within the compact nanofiber geometry. Furthermore, bio-compatible light-emitting nanofibers prepared by a cost-effective solution-based processing are very promising platforms for biophotonic applications such as fluorescence sensing and imaging.

  5. Saturation phenomenon research of fast light in a Tm3+-doped optical fiber at room temperature

    NASA Astrophysics Data System (ADS)

    Qiu, Wei; Liu, Jianjun; Wang, Yuda; Yang, Yujing; Lv, Pin; Jiang, Qiuli

    2017-09-01

    The theoretical model and numerical simulations are established by the rate equation of thulium ion. Using the coherent population oscillation effect, we realize the controllable light velocity in the thulium doped fiber. We show that coherent population oscillations effect produces a very narrow spectral hole and anti-holes in the spectrum. The hole caused the amplitude modulation beam experience a large change of the group of refractive index, and makes us to achieve fast light propagation. Therefore, the pump intensity can be used as a control parameter to increase the fractional advance. In addition, we can confirm that the larger input intensity can lead to large time advancement, and saturation phenomenon of fast light exists in low frequency.

  6. Enhanced photoluminescence of Si nanocrystals-doped cellulose nanofibers by plasmonic light scattering

    NASA Astrophysics Data System (ADS)

    Sugimoto, Hiroshi; Zhang, Ran; Reinhard, Björn M.; Fujii, Minoru; Perotto, Giovanni; Marelli, Benedetto; Omenetto, Fiorenzo G.; Dal Negro, Luca

    2015-07-01

    We report the development of bio-compatible cellulose nanofibers doped with light emitting silicon nanocrystals and Au nanoparticles via facile electrospinning. By performing photoluminescence (PL) spectroscopy as a function of excitation wavelength, we demonstrate plasmon-enhanced PL by a factor of 2.2 with negligible non-radiative quenching due to plasmon-enhanced scattering of excitation light from Au nanoparticles to silicon nanocrystals inside the nanofibers. These findings provide an alternative approach for the development of plasmon-enhanced active systems integrated within the compact nanofiber geometry. Furthermore, bio-compatible light-emitting nanofibers prepared by a cost-effective solution-based processing are very promising platforms for biophotonic applications such as fluorescence sensing and imaging.

  7. Double-doped TiO2 nanoparticles as an efficient visible-light-active photocatalyst and antibacterial agent under solar simulated light

    NASA Astrophysics Data System (ADS)

    Ashkarran, Ali Akbar; Hamidinezhad, Habib; Haddadi, Hedayat; Mahmoudi, Morteza

    2014-05-01

    Silver and nitrogen doped TiO2 nanoparticles (NPs) were synthesized via sol-gel method. The physicochemical properties of the achieved NPs were characterized by various methods including X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultra violet-visible absorption spectroscopy (UV-vis). Both visible-light photocatalytic activity and antimicrobial properties were successfully demonstrated for the degradation of Rhodamine B (Rh. B.), as a model dye, and inactivation of Escherichia coli (E. coli), as a representative of microorganisms. The concentration of the employed dopant was optimized and the results revealed that the silver and nitrogen doped TiO2 NPs extended the light absorption spectrum toward the visible region and significantly enhanced the photodegradation of model dye and inactivation of bacteria under visible-light irradiation while double-doped TiO2 NPs exhibited highest photocatalytic and antibacterial activity compared with single doping. The significant enhancement in the photocatalytic activity and antibacterial properties of the double doped TiO2 NPs, under visible-light irradiation, can be attributed to the generation of two different electronic states acting as electron traps in TiO2 and responsible for narrowing the band gap of TiO2 and shifting its optical response from UV to the visible-light region.

  8. Controlling Proton Conductivity with Light: A Scheme Based on Photoacid Doping of Materials.

    PubMed

    Haghighat, Shima; Ostresh, Sarah; Dawlaty, Jahan M

    2016-02-11

    Transducing light energy to changes in material properties is central to a large range of functional materials, including those used in light harvesting. In conventional semiconductors, photoconductivity arises due to generation of mobile electrons or holes with light. Here we demonstrate, to our knowledge for the first time, an analogue of this effect for protons in an organic polymer solution and in water. We show that when a material is doped with photoacids, light excitation generates extra mobile protons that change the low-frequency conductivity of the material. We measure such change both in poly(ethylene glycol) (PEG) and in water sandwiched between two transparent electrodes and doped with a well-known photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). The complex impedance of the material is measured over a range of 0.1 Hz-1 MHz in both the presence and absence of light, and it is found that shining light changes the low frequency impedance significantly. We model the impedance spectra of the material with a minimal circuit composed of a diffusive impedance (Warburg element), a parallel capacitance, and a resistance. Fitting the light and dark impedance spectra to the model reveals that light reduces the low-frequency diffusive impedance of the material, which is consistent with generation of extra free carriers by light. We further suggest that the light-induced conductivity change arises mainly due to those photoreleased protons that manage to escape the zone of influence of the parent ion and avoid recapture. Such escape is more likely in materials with larger diffusion coefficient for protons and shorter electrostatic screening lengths for the parent ion. This explanation is consistent with our observed differences in the photoconductivity of solution of HPTS in water and in PEG. We anticipate that this scheme can be employed in protonic circuits where direct transduction of energy from light to protonic gradients or protonic currents is

  9. Impact of source/drain and bulk engineering on LFN performance of n- and p-MOSFET

    NASA Astrophysics Data System (ADS)

    Ioannidis, E. G.; Rohracher, K.; Roger, F.; Pflanzl, W. C.; Leisenberger, F. P.; Wachmann, E.; Seebacher, E.; Vescoli, V.

    2017-09-01

    In this paper, we present a detailed investigation of the impact of different Lightly Doped Drain (LDD) implants and different well doping on the low frequency noise performance of n- and p-MOS devices from a CMOS technology node. We investigate the impact of three different devices. Two with the same LDD implant but different well doping and one with different LDD implant cocktail. The results demonstrate that the different bulk doping does not affect the low frequency noise performance of the devices. On the other hand there is a serious impact on the noise level of the device with the different LDD implant. In order to further support our results we investigated devices with different lengths in the linear and saturation region of operation.

  10. Visible light emission and energy transfer processes in Sm-doped nitride films

    SciTech Connect

    Zanatta, A. R.

    2012-06-15

    Even though the great interest in studying the near-infrared light emission due to Er{sup 3+} ions for telecommunication purposes, efficient visible radiation can be achieved from many different rare-earth (RE) ions. In fact, visible and/or near-infrared light emission takes place in RE-doped wide bandgap semiconductors following either photon or electron excitation, suggesting their technological potential in devices such as light-emitting diodes (LED's) and flat-panel displays, for example. Taking into consideration these aspects, the present contribution reports on the investigation of AlN, BeN, GeN, and SiN thin films doped with samarium. The samples were prepared by sputtering and as a result of the deposition method and conditions they present an amorphous structure and Sm concentrations in the low 0.5 at. %. After deposition, the samples were submitted to thermal annealing treatments and investigated by different spectroscopic techniques. A detailed examination of the experimental data allowed to identify optical transitions due to Sm{sup 3+} and Sm{sup 2+} ions as well as differences in their mechanisms of photon excitation and recombination. Moreover, it is shown that the Sm-related spectral features and emission intensity are susceptible, respectively, to the atomic environment the Sm{sup 3+}/Sm{sup 2+} ions experience and to the presence of non-radiative recombination centers.

  11. Visible light emission and energy transfer processes in Sm-doped nitride films

    NASA Astrophysics Data System (ADS)

    Zanatta, A. R.

    2012-06-01

    Even though the great interest in studying the near-infrared light emission due to Er3+ ions for telecommunication purposes, efficient visible radiation can be achieved from many different rare-earth (RE) ions. In fact, visible and/or near-infrared light emission takes place in RE-doped wide bandgap semiconductors following either photon or electron excitation, suggesting their technological potential in devices such as light-emitting diodes (LED's) and flat-panel displays, for example. Taking into consideration these aspects, the present contribution reports on the investigation of AlN, BeN, GeN, and SiN thin films doped with samarium. The samples were prepared by sputtering and as a result of the deposition method and conditions they present an amorphous structure and Sm concentrations in the low 0.5 at. %. After deposition, the samples were submitted to thermal annealing treatments and investigated by different spectroscopic techniques. A detailed examination of the experimental data allowed to identify optical transitions due to Sm3+ and Sm2+ ions as well as differences in their mechanisms of photon excitation and recombination. Moreover, it is shown that the Sm-related spectral features and emission intensity are susceptible, respectively, to the atomic environment the Sm3+/Sm2+ ions experience and to the presence of non-radiative recombination centers.

  12. Large magnetic field effects in electrochemically doped organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    van Reenen, S.; Kersten, S. P.; Wouters, S. H. W.; Cox, M.; Janssen, P.; Koopmans, B.; Bobbert, P. A.; Kemerink, M.

    2013-09-01

    Large negative magnetoconductance (MC) of ˜12% is observed in electrochemically doped polymer light-emitting diodes at sub-band-gap bias voltages (Vbias). Simultaneously, a positive magnetoefficiency (Mη) of 9% is observed at Vbias = 2 V. At higher bias voltages, both the MC and Mη diminish while a negative magnetoelectroluminescence (MEL) appears. The negative MEL effect is rationalized by triplet-triplet annihilation that leads to delayed fluorescence, whereas the positive Mη effect is related to competition between spin mixing and exciton formation leading to an enhanced singlet:triplet ratio at nonzero magnetic field. The resultant reduction in triplet exciton density is argued to reduce detrapping of polarons in the recombination zone at low-bias voltages, explaining the observed negative MC. Regarding organic magnetoresistance, this study provides experimental data to verify existing models describing magnetic field effects in organic semiconductors, which contribute to better understanding hereof. Furthermore, we present indications of strong magnetic field effects related to interactions between trapped carriers and excitons, which specifically can be studied in electrochemically doped organic light-emitting diodes (OLEDs). Regarding light-emitting electrochemical cells (LECs), this work shows that delayed fluorescence from triplet-triplet annihilation substantially contributes to the electroluminescence and the device efficiency.

  13. The visible light absorption property of Cu-doped hydrogen titanate nanotube thin films: An experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    An, Yongliang; Li, Zhonghua; Shen, Jun

    2013-11-01

    Hydrogen titanate nanotube thin films were synthesized by alkaline hydrothermal method using titanium plates as starting material and then doped with Cu through ion-exchange method. The experimental results show that Cu ions incorporate into the walls of nanotubes and exist as Cu2+. Cu doping leads to a red shift of the optical absorption edge from the ultraviolet region to the visible light region. First-principles calculation results reveal that Cu doping substantially reduces the band gap of hydrogen titanate nanotubes due to the presence of the impurity energy band of Cu 3d in intrinsic band gap. The valence and conduction band positions of Cu-doped hydrogen titanate nanotubes were determined by valence band spectra. The valence band is shifted to lower potential while the conduction band is shifted to higher potential after Cu doping, explaining the origin of the band gap narrowing and red shift.

  14. Enhanced dopant solubility and visible-light absorption in Cr-N co-doped TiO2 nanoclusters

    SciTech Connect

    Chiodi, Dr Mirco; Cheney, Christine; Vilmercati, Paolo; Cavaliere, Emanuele; Mannella, Norman; Gavioli, Luca; Weitering, Harm H

    2012-01-01

    A major obstacle toward employing TiO2 as an efficient photoactive material is related to its large optical band gap, strongly limiting visible light absorption. Substitutional doping with both donors and acceptors (co-doping) potentially leads to a significant band gap reduction, but the effectiveness of the co-doping approach remains limited by the low solubility of dopants inside TiO2. Here we show that nanostructured Cr and N co-doped TiO2 thin films can be obtained by Supersonic Cluster Beam Deposition (SCBD) with a high concentration of dopants and a strongly reduced band gap. Complementary spectroscopic investigations show that doping effectively occurs into substitutional lattice sites, inducing dopant levels in the gap that are remarkably delocalized. The high surface-to-volume ratio, typical of SCBD nanostructured films, likely facilitates the dopant incorporation. The present results indicate that SCBD films are highly promising photoactive nanophase materials.

  15. The enhanced visible light photocatalytic activity of yttrium-doped BiOBr synthesized via a reactable ionic liquid

    NASA Astrophysics Data System (ADS)

    He, Minqiang; Li, Weibing; Xia, Jiexiang; Xu, Li; Di, Jun; Xu, Hui; Yin, Sheng; Li, Huaming; Li, Mengna

    2015-03-01

    Yttrium (Y)-doped BiOBr with different Y doping concentrations has been synthesized via solvothermal method in the presence of reactable ionic liquid 1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br). Their structures, morphologies and optical properties were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activities of the yttrium doped BiOBr samples were evaluated by the degradation of ciprofloxacin (CIP) and rhodamine B (RhB) under visible-light irradiation. The yttrium doped BiOBr exhibited enhanced photocatalytic activity for the degradation of the two types of pollutants, and the 5wt%Y-doped BiOBr showed the highest photocatalytic activity. The enhanced photocatalytic performance could be attributed to the reduced band gap and improved separation of electron-hole pairs.

  16. High performance B doped BiVO4 photocatalyst with visible light response by citric acid complex method.

    PubMed

    Wang, Min; Zheng, Haoyan; Liu, Qiong; Niu, Chao; Che, Yinsheng; Dang, Mingyan

    2013-10-01

    A B-doped BiVO4 photocatalyst was synthesized by citric acid complex method and using H3BO3 as the dopant source, and the photocatalyst was characterized with XPS, XRD, SEM, BET and UV-Vis DRS. The photocatalytic activity was evaluated by the photocatalytic degradation of a methyl orange (MO) solution under visible light. This assay revealed that both the pure BiVO4 and all of the B doped samples were the monoclinic phase. Doping the BiVO4 with B increased the number of V(4+) and oxygen vacancies, which led to the red shift of the absorbing boundary of the B-doped BiVO4 but had little influence on the morphology and crystal size. The B doping improved the photocatalytic activity, and the highest photocatalytic degradation rate of 98% occurred with a B dopant concentration of 0.04. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. High performance B doped BiVO4 photocatalyst with visible light response by citric acid complex method

    NASA Astrophysics Data System (ADS)

    Wang, Min; Zheng, Haoyan; Liu, Qiong; Niu, Chao; Che, Yinsheng; Dang, Mingyan

    2013-10-01

    A B-doped BiVO4 photocatalyst was synthesized by citric acid complex method and using H3BO3 as the dopant source, and the photocatalyst was characterized with XPS, XRD, SEM, BET and UV-Vis DRS. The photocatalytic activity was evaluated by the photocatalytic degradation of a methyl orange (MO) solution under visible light. This assay revealed that both the pure BiVO4 and all of the B doped samples were the monoclinic phase. Doping the BiVO4 with B increased the number of V4+ and oxygen vacancies, which led to the red shift of the absorbing boundary of the B-doped BiVO4 but had little influence on the morphology and crystal size. The B doping improved the photocatalytic activity, and the highest photocatalytic degradation rate of 98% occurred with a B dopant concentration of 0.04.

  18. Slow and fast light propagation in a defect slab doped with polaritonic materials and nanoparticles

    NASA Astrophysics Data System (ADS)

    Solookinejad, Gh; Jabbari, M.; Panahi, M.; Ahmadi Sangachin, E.

    2016-12-01

    In this paper, the group velocity of transmitted and reflected pulses through a defect dielectric medium doped with polaritonic materials and nanoparticles is explored by using the density matrix equations and transform matrix method. It is demonstrated that the group velocity of transmitted and reflected lights can be manipulated by adjusting the system’s parameters. The effect of the dipole-dipole interaction is also discussed on behaviors of transmitted and reflected pulses through the slab. Our proposed model may be opened up the possibility of new storage and switching devices based on polaritonic material nanoparticles in future commercial systems.

  19. Enhancement of Quantum Efficiency of Organic Light Emitting Devices by Doping Magnetic Nanoparticles

    SciTech Connect

    Sun, Chengjun; Wu, Yue; Xu, Zhihua; Hu, Bin; Bai, Jianmin; Wang, Jian-Ping; Shen, Jian

    2007-01-01

    Magnetic nanoparticles of CoFe are used as dopants to enhance the quantum efficiency of electroluminance in a single layer organic light emitting device (OLED). The enhancement of quantum efficiency increases with both increasing density of CoFe nanoparticles and external magnetic field. For a given OLED with 0.1 wt % doping, the enhancement of the quantum efficiency reaches {approx}27% and {approx}32% without and with a magnetic field, respectively. The origin of these improvements could be attributed to the simultaneous increases of the portion of excitons among total charge carriers and the fraction of singlets among the total excitons

  20. Efficient Triplet Exciton Fusion in Molecularly Doped Polymer Light-Emitting Diodes.

    PubMed

    Di, Dawei; Yang, Le; Richter, Johannes M; Meraldi, Lorenzo; Altamimi, Rashid M; Alyamani, Ahmed Y; Credgington, Dan; Musselman, Kevin P; MacManus-Driscoll, Judith L; Friend, Richard H

    2017-04-01

    Solution-processed polymer organic light-emitting diodes (OLEDs) doped with triplet-triplet annihilation (TTA)-upconversion molecules, including 9,10-diphenylanthracene, perylene, rubrene and TIPS-pentacene, are reported. The fraction of triplet-generated electroluminescence approaches the theoretical limit. Record-high efficiencies in solution-processed OLEDs based on these materials are achieved. Unprecedented solid-state TTA-upconversion quantum yield of 23% (TTA-upconversion reaction efficiency of 70%) at electrical excitation well below one-sun equivalent is observed.

  1. ZIF-8 derived porous N-doped ZnO with enhanced visible light-driven photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Feng, Yi; Lu, Haiqiang; Gu, Xiaoli; Qiu, Jianhao; Jia, Mingmin; Huang, Chaobo; Yao, Jianfeng

    2017-03-01

    A facile and simple method was offered to synthesize porous N-doped ZnO via direct calcination of urea and ZIF-8 mixture. From XRD and XPS analysis, nitrogen has been successfully incorporated into ZnO lattices without introducing other N-containing or Zn-containing phases. Such nitrogen doping can enhance the visible-light harvesting ability and inhibit the recombination rate of electron-hole pairs; as a result, improved visible-light driven photocatalytic activity was achieved in N-doped porous ZnO and the photocatalytic activity of N-doped ZnO is 2.58 times higher than that of ZIF-derived pure ZnO.

  2. P-doped TiO2 with superior visible-light activity prepared by rapid microwave hydrothermal method

    NASA Astrophysics Data System (ADS)

    Niu, Jinfen; Lu, Pan; Kang, Mei; Deng, Kunfa; Yao, Binghua; Yu, Xiaojiao; Zhang, Qian

    2014-11-01

    Phosphorous-doped anatase TiO2 powders (P-TiO2) were prepared by rapid microwave hydrothermal method. The resulting materials were characterized by XRD, SEM, XPS, DRS and N2 adsorption. P-doping decreased the band gap and enlarged the surface area of P-doped samples than that of undoped TiO2 samples. Therefore, the photocatalytic degradation of methyl blue (MB) and tetracycline hydrochloride (Tc) experiments showed that the P-TiO2 catalysts, especially the two-steps-controlling products P-TiO2-2, exhibited higher degradation efficiency than the undoped TiO2 and commercial P25 under visible-light irradiation. Hydroxyl radicals (rad OH) have been confirmed to be the active species during the photocatalytic oxidation reaction. The microwave hydrothermal method confirms to be very suitable for the synthesis of superior visible-light activity P-doped samples.

  3. Bistable light shutter using dye-doped liquid crystals for a see-through display

    NASA Astrophysics Data System (ADS)

    Huh, Jae-Won; Heo, Joon; Yu, Byeong-Huh; Yoon, Tae-Hoon

    2016-03-01

    See-through displays have got high attention as one of the next generation display devices. Especially, see-through displays that use organic light-emitting diodes (OLEDs) and liquid crystal displays (LCDs) have been actively studied. However, a see-through display using OLEDs cannot provide black color because of their see-through area. Although a see-through display using LCDs can provide black color with crossed polarizers, it cannot block the background. This inevitable problem can be solved by placing a light shutter at the back of a see-through display. To maintain the transparent or opaque state, an electric field must be applied to a light shutter. To achieve low power consumption, a bistable light shutter using polymer-stabilized cholesteric liquid crystals (CLC) has been proposed. It is switchable between the translucent and transparent states only. Therefore, it cannot provide black color. Moreover, it cannot block the background perfectly because of poor performance in the translucent state. In this work we will introduce a bistable light shutter using dye-doped CLCs. To improve the electro-optic characteristics in the opaque state, we employed a crossed electrode structure instead of a parallel one. We will demonstrate that the light shutter can exhibit stable bistable operation between the transparent homeotropic and opaque focal-conic states thanks to polymer stabilization.

  4. Effect of a delta-doping green emitting layer in white organic light-emitting device

    NASA Astrophysics Data System (ADS)

    Zhao, Juan; Yu, Junsheng; Jiang, Yadong

    2012-10-01

    White organic light-emitting devices (WOLEDs) based on a double-emitting layer (EML) structure were fabricated, while phosphorescent blue and yellow emitters were employed. An ultra-thin layer of non-doped green tris(2-phenylpyridine) iridium [Ir(ppy)3], which was considered as delta-doping layer, was inserted between the two EMLs for optimization. Furthermore, effect of adjusting thickness of this thin layer on device performance was studied. The results showed that the optimized WOLED consisting of 1-nm Ir(ppy)3 EML achieved a maximum luminance of 29,100 cd/m2, maximum external quantum efficiency of 7%, maximum current efficiency of 25.3 cd/A and maximum power efficiency of 7.8 lm/W, together with low efficiency roll-off over a wide luminance range. Meanwhile, the white emission with Commission Internationale del'Eclariage (CIE) coordinates of (0.382,0.446) at a driving voltage of 10 V were observed. The performance enhancement is ascribed to improved charge carrier balance through introduction the highly efficient Ir(ppy)3 as the thin delta-doping layer.

  5. Enhanced photocatalytic activity of cadmium-doped Bi2WO6 nanoparticles under simulated solar light

    NASA Astrophysics Data System (ADS)

    Song, Xu Chun; Li, Wen Ting; Huang, Wan Zhen; Zhou, Huan; Yin, Hao Yong; Zheng, Yi Fan

    2015-03-01

    Novel cadmium-doped Bi2WO6 nanoparticles with different Cd contents have been synthesized by a one-step route using ethylene glycol and water as solvents at 180 °C for 12 h. The as-synthesized samples were characterized in detailed by SEM, XRD, EDS, HRTEM, UV-Vis DRS, BET techniques, and so on. The results shown that with the increase of the Cd2+ addition, the crystal structure, lattice space, and absorption edge were not significantly changed and the calculated band gap value was 2.58 eV. However, the flower-like Bi2WO6 sphere was gradually destroyed. Simultaneously, the surface area and photocurrent responses of the catalysts were greatly increased. Photocatalytic activity of the Cd-doped Bi2WO6 samples was determined by monitoring the change of RhB concentration under simulated solar light. The results revealed that cadmium doping greatly improved the photocatalytic efficiency of Bi2WO6. The Bi2WO6 sample with R Cd = 0.05 displayed the highest photocatalytic activity, and the degradation rate is about two times greater than pure Bi2WO6. Moreover, the Cd-Bi2WO6 photocatalyst remained stable even after five consecutive cycles. A possible mechanism of photocatalytic activity enhancement on basis of the experimental results was proposed.

  6. In-situ monitoring of slow light structures in dye-doped polymer waveguide materials

    NASA Astrophysics Data System (ADS)

    McKenna, Edward M., Jr.; Lin, Andy; Waskiewicz, Alex; Mickelson, Alan R.

    2007-09-01

    In this work, we describe a technique for positioning the passband and monitoring the slowing factor of Moiré gratings written into PMMA-DR1 waveguides during fabrication. Slow light structures made with material platforms such as silicon must fabricated before their actual slowing properties can be measured. In our dye doped polymer waveguides, the slowing can be decided beforehand and the fabrication controlled to achieve the desired performance figure. The resulting group velocity slowing in the composite waveguide can be controlled by varying the index contrast of the grating. In dye-doped polymer materials we use, the index contrast can be changed using the process of irreversible photobleaching. Our technique uses a broadband source to monitor the reflectance spectrum of the grating and the delay of the structure is determined from this measurement. The theory behind the technique is reviewed and results are presented for a Moiré grating written into waveguides fabricated in the dye-doped polymer material system, PMMA-DR1.

  7. High-Performance Organic Light Emitting Diode with Substitutionally Boron-doped Graphene Anode.

    PubMed

    Wu, Tien-Lin; Yeh, Chao-Hui; Hsiao, Wen-Ting; Huang, Pei-Yun; Huang, Min-Jie; Chiang, Yen-Hsin; Cheng, Chien-Hong; Liu, Rai-Shung; Chiu, Po-Wen

    2017-04-07

    Hole injection barrier between anode and hole injection layer is of critical importance to determine the device performance of organic light-emitting diodes (OLEDs). Here, we report on a record-high external quantum efficiency (24.6 % in green phosphorescence) of OLEDs fabricated on both rigid and flexible substrates, with the performance enhanced by the use of nearly defect-free and high-mobility boron-doped graphene as an effective anode and hexaazatriphenylene hexacarbonitrile as a new type of hole injection layer. This new structure outperforms the existing graphene-based OLEDs, in which MoO3, AuCl3, or bis(trifluoromethanesulfonyl)amide (TFSA) are typically used as a doping source for p-type graphene. The improvement of the OLED performance is attributed mainly to the appreciable increase of hole conductivity in nearly defect-free boron-doped monolayer graphene, along with the high work function achieved by the use of newly developed hydrocarbon precursor containing boron in the graphene growth by chemical vapor deposition.

  8. Preparation of N-doped ZnO-loaded halloysite nanotubes catalysts with high solar-light photocatalytic activity.

    PubMed

    Cheng, Zhi-Lin; Sun, Wei

    2015-01-01

    N-doped ZnO nanoparticles were successfully assembled into hollow halloysite nanotubes (HNTs) by using the impregnation method. The catalysts based on N-doped ZnO-loaded HNTs nanocomposites (N-doped ZnO/HNTs) were characterized by X-ray diffraction (XRD), transmission electron microscopy-energy dispersive X-ray (TEM-EDX), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), UV-vis and Fourier transform infrared spectroscopy (FT-IR) techniques. The XRD pattern showed ZnO nanoparticles with hexagonal structure loaded on HNTs. The TEM-EDX analysis indicated ZnO particles with the crystal size of ca.10 nm scattered in hollow structure of HNTs, and furthermore the concentration of N atom in nanocomposites was up to 2.31%. The SEM-EDX verified most of N-ZnO nanoparticles existing in hollow nanotubes of HNTs. Besides containing an obvious ultraviolet absorbance band, the UV-vis spectra of the N-doped ZnO/HNTs catalysts showed an available visible absorbance band by comparing to HNTs and non-doped ZnO/HNTs. The photocatalytic activity of the N-doped ZnO/HNTs catalysts was evaluated by the degradation of methyl orange (MO) solution with the concentration of 20 mg/L under the simulated solar-light irradiation. The result showed that the N-doped ZnO/HNTs catalyst exhibited a desirable solar-light photocatalytic activity.

  9. Magnetic dispersion of the diagonal incommensurate phase in lightly doped La2-xSrxCuO4.

    PubMed

    Matsuda, M; Fujita, M; Wakimoto, S; Fernandez-Baca, J A; Tranquada, J M; Yamada, K

    2008-11-07

    We present inelastic neutron scattering experiments on a single-domain crystal of lightly doped La1.96Sr0.04CuO4. We find that the magnetic excitation spectrum in this insulating phase with a diagonal incommensurate spin modulation is remarkably similar to that in the superconducting regime, where the spin modulation is bond parallel. In particular, we find that the dispersion slope at low energy is essentially independent of doping and temperature over a significant range. The energy at which the excitations cross the commensurate antiferromagnetic wave vector increases roughly linearly with doping through the underdoped regime.

  10. Ultrastrong light-matter coupling in electrically doped microcavity organic light emitting diodes

    SciTech Connect

    Mazzeo, M.; Genco, A.; Gambino, S.; Ballarini, D.; Mangione, F.; Sanvitto, D.; Di Stefano, O.; Patanè, S.; Savasta, S.; Gigli, G.

    2014-06-09

    The coupling of the electromagnetic field with an electronic transition gives rise, for strong enough light-matter interactions, to hybrid states called exciton-polaritons. When the energy exchanged between light and matter becomes a significant fraction of the material transition energy an extreme optical regime called ultrastrong coupling (USC) is achieved. We report a microcavity embedded p-i-n monolithic organic light emitting diode working in USC, employing a thin film of squaraine dye as active layer. A normalized coupling ratio of 30% has been achieved at room temperature. These USC devices exhibit a dispersion-less angle-resolved electroluminescence that can be exploited for the realization of innovative optoelectronic devices. Our results may open the way towards electrically pumped polariton lasers.

  11. Effect of Stepwise Doping on Lifetime and Efficiency of Blue and White Phosphorescent Organic Light Emitting Diodes.

    PubMed

    Lee, Song Eun; Lee, Ho Won; Lee, Seok Jae; Koo, Ja-ryong; Lee, Dong Hyung; Yang, Hyung Jin; Kim, Hye Jeong; Yoon, Seung Soo; Kim, Young Kwan

    2015-02-01

    We investigated a light emission mechanism of blue phosphorescent organic light emitting diodes (PHOLEDs), using a stepwise doping profile of 2, 8, and 14 wt.% within the emitting layer (EML). We fabricated several blue PHOLEDs with phosphorescent blue emitter iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C2]picolinate doped in N,N'-dicarbazolyl-3,5-benzene as a p-type host material. A blue PHOLED with the highest doping concentration as part of the EML close to an electron transporting layer showed a maximum luminous efficiency of 20.74 cd/A, and a maximum external quantum efficiency of 10.52%. This can be explained by effective electron injection through a highly doped EML side. Additionally, a white OLED based on the doping profile was fabricated with two thin red EMLs within a blue EML maintaining a thickness of 30 nm for the entire EML. Keywords: Blue Phosphorescent Organic Light Emitting Diodes, Stepwise Doping Structure, Charge Trapping Effect.

  12. Hydrothermal derived nitrogen doped SrTiO3 for efficient visible light driven photocatalytic reduction of chromium(VI).

    PubMed

    Xing, Guanjie; Zhao, Lanxiao; Sun, Tao; Su, Yiguo; Wang, Xiaojing

    2016-01-01

    In this work, we report on the synthesis of nitrogen doped SrTiO3 nanoparticles with efficient visible light driven photocatalytic activity toward Cr(VI) by the solvothermal method. The samples are carefully characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy and photocatalytic test. It is found that nitrogen doping in SrTiO3 lattice led to an apparent lattice expansion, particle size reduction as well as subsequent increase of Brunner-Emmet-Teller surface area. The visible light absorption edge and intensity can be modulated by nitrogen doping content, which absorption edge extends to about 600 nm. Moreover, nitrogen doping can not only modulate the visible light absorption feature, but also have consequence on the enhancement of charge separation efficiency, which can promote the photocatalytic activity. With well controlled particle size, Brunner-Emmet-Teller surface area, and electronic structure via nitrogen doping, the photocatalytic performance toward Cr(VI) reduction of nitrogen doped SrTiO3 was optimized at initial hexamethylenetetramine content of 2.

  13. Photocatalytic activity under UV/Visible light range of Nb-doped titanate nanostructures synthesized with Nb oxide

    NASA Astrophysics Data System (ADS)

    Byun, Jong Min; Choi, Hye Rim; Kim, Young Do; Sekino, Tohru; Kim, Se Hoon

    2017-09-01

    In this work, using economical and stable niobium oxide (Nb2O5) powder as niobium source, visible light responsive Nb-doped titanate nanostructures were synthesized by hydrothermal process. The synthesized Nb-doped titanate nanostructures were composed of two types of titanate nanostructures (nanotubes and nanosheets) and TiO2 nanoparticles. They have a smaller band gap energy of 3.24 eV compared to pure TNTs that were synthesized under the same experimental conditions. The photocatalytic activity of the synthesized Nb-doped titanate nanostructures was evaluated under visible light irradiation through the degradation of methylene blue (MB) and rhodamine B (RhB). Consequently, the synthesized Nb-doped titanate nanostructures exhibited much higher photocatalytic activity under visible light irradiation than pure TNTs. The photocatalytic activity of the synthesized Nb-doped titanate nanostructures was 1.4 times (MB) and 3.1 times (RhB) higher than of pure TNTs because the Nb-doping narrowed the band gap and it accelerated the separation of photo-induced electron-hole pairs.

  14. Self-doping and surface plasmon modification induced visible light photocatalysis of BiOCl

    NASA Astrophysics Data System (ADS)

    Jiang, Jing; Zhang, Lizhi; Li, Hao; He, Weiwei; Yin, Jun Jie

    2013-10-01

    In this study we demonstrate that self-doping and surface plasmon resonance could endow a wide-band-gap ternary semiconductor BiOCl with remarkable visible light driven photocatalytic activity on the degradation of organic pollutants and photocurrent generation properties. The self-doped BiOCl with plasmonic silver modification was synthesized by a facile one-pot nonaqueous approach and systematically characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-visible diffuse reflectance spectra, electron spin resonance, and X-ray photoelectron spectroscopy. The photocurrent enhancement was found to be intimately dependent on the irradiation wavelength and matched well with the intensity of the absorption of the Ag nanoparticles. Reactive species trapping experiments and electron spin resonance spectroscopy with 5,5-dimethyl-1-pyrroline-N-oxide spin-trapping adducts confirmed that more oxidative species could be generated from the photogenerated electrons due to the plasmon-excitation of the metallic Ag in the self-doped BiOCl with plasmonic silver modification, which is responsible for the great enhancement of photocatalytic activity and photocurrent. Surface photovoltage spectroscopy and time-resolved photoluminescence spectroscopy results revealed the transfer of plasmon-band-induced electrons from Ag nanoparticles into BiOCl and the acceleration effect of surface plasmon resonance-induced intense oscillating electric fields on this electron transfer. This study would not only provide direct evidence of plasmonic photocatalysis, but also shed light on the design of highly efficient metal-semiconductor composite photocatalysts.In this study we demonstrate that self-doping and surface plasmon resonance could endow a wide-band-gap ternary semiconductor BiOCl with remarkable visible light driven photocatalytic activity on the degradation of organic pollutants and photocurrent generation properties. The self-doped Bi

  15. Thermo-optical and polarized light studies of MWCNT doped PDLCs

    NASA Astrophysics Data System (ADS)

    Mahajan, Jyoti; Gupta, Sureshchandra J.; Saxena, S.; Swati, K.

    2016-05-01

    Optical properties of liquid crystals (LCs) are very essential in an understanding of the technological applications of the LCs. Polymer Dispersed Liquid Crystals (PDLCs) are prepared by dispersing the liquid crystal droplets in polymer matrix. Experiments to study thermo-optical properties and polarized light studies are considered in the present work. PDLCs used in the present work are composed of poly (methyl methacrylate) and cholestric liquid crystal namely cholesteryl propionate. These are further doped with Multi-walled carbon Nanotubes (MWCNTs). Thermo-optical study reveals that there is decrease in the nematic-isotropic phase transition temperature (Clearing point temperature i.e. CPT) with increase in the concentration of MWCNTs. The effect of polarized light is studied by means of change in polarization which is characteristic of the material properties. The optical constants graphs obtained from ellipsometry provides the possibility of the use of composite material for optical switching systems.

  16. Static and dynamic photoinduced magnetic effects in yttrium-iron garnet lightly doped with barium ions

    SciTech Connect

    Vorob'eva, N. V. Khalilov, R. Z.

    2012-04-15

    In yttrium-iron garnet lightly doped with barium, direct measurements of the photoinduced changes in magnetostrictive strains disagree with those in magnetostriction constants at 78-100 K. This is attributed to a considerable photoinduced modification of the initial state in this sample due to a redistribution of the charge (during illumination) between cations of the ferromagnetic octahedral sublattice. In the same sample, the temperature dependence of the photoinduced disaccomodation of magnetic permeability characterizing the initial demagnetized state is measured and calculated. A change in the electron mechanism of the phenomenon during the transition to room temperature is shown. The conclusion about the promising prospects for using such samples for remagnetization by light is advanced.

  17. The formation of light emitting cerium silicates in cerium-doped silicon oxides

    SciTech Connect

    Li Jing; Zalloum, Othman; Roschuk, Tyler; Heng Chenglin; Wojcik, Jacek; Mascher, Peter

    2009-01-05

    Cerium-doped silicon oxides with cerium concentrations of up to 0.9 at. % were deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition. Bright cerium related photoluminescence, easily seen even under room lighting conditions, was observed from the films and found to be sensitive to film composition and annealing temperature. The film containing 0.9 at. % Ce subjected to anneal in N{sub 2} at 1200 deg. C for 3 h showed the most intense cerium-related emission, easily visible under bright room lighting conditions. This is attributed to the formation of cerium silicate [Ce{sub 2}Si{sub 2}O{sub 7} or Ce{sub 4.667} (SiO{sub 4}){sub 3}O], the presence of which was confirmed by high resolution transmission electron microscopy.

  18. Enhanced photocatalytic performance of boron doped Bi₂WO₆ nanosheets under simulated solar light irradiation.

    PubMed

    Fu, Yu; Chang, Chun; Chen, Peng; Chu, Xiaolong; Zhu, Lingyan

    2013-06-15

    Bi₂WO6 doped with different amounts of boron atoms (0.1, 0.5, 1.0, 5.0 and 10% B) were synthesized using hydrothermal method and their photocatalytic activities to degrade rhodamine B (RhB) under simulated solar light was investigated. The successful incorporation of B atoms in Bi₂WO₆ was proved by FT-IR, Raman spectra and XPS. Doping with B could affect the pore structure and volume. 0.5% B/Bi₂WO₆ displayed more mesopores with higher total pore volume than pure Bi₂W₆; while the pores of 10% B/Bi₂WO₆ mainly distributed in microporous range with much less total pore volume. As a result, 0.5% B/Bi₂WO₆ displayed stronger adsorption capacity to RhB, favoring the photodegradation. In addition, the doped B atoms could act as electron traps and facilitate the separation of photogenerated electron-hole pairs due to its electron deficient and oxytropic characteristics. 0.5% B/Bi₂WO₆ displayed the highest photocatalytic activity under simulated solar light with rate constant (kobs) 8.8 times of that using pure Bi₂WO₆. Its photoactivity was affected by solution pH and the optimum was achieved at pH 7. At this condition, around 100% of RhB (10(-5)mol/L) was degraded in 180 min. The photogenerated holes were the main active species responsible for the photodegradation of RhB by B/Bi₂WO₆.

  19. Tuning the emission of ZnO nanorods based light emitting diodes using Ag doping

    NASA Astrophysics Data System (ADS)

    Echresh, Ahmad; Chey, Chan Oeurn; Shoushtari, Morteza Zargar; Nur, Omer; Willander, Magnus

    2014-11-01

    We have fabricated, characterized, and compared ZnO nanorods/p-GaN and n-Zn0.94Ag0.06O nanorods/p-GaN light emitting diodes (LEDs). Current-voltage measurement showed an obvious rectifying behaviour of both LEDs. A reduction of the optical band gap of the Zn0.94Ag0.06O nanorods compared to pure ZnO nanorods was observed. This reduction leads to decrease the valence band offset at n-Zn0.94Ag0.06O nanorods/p-GaN interface compared to n-ZnO nanorods/p-GaN heterojunction. Consequently, this reduction leads to increase the hole injection from the GaN to the ZnO. From electroluminescence measurement, white light was observed for the n-Zn0.94Ag0.06O nanorods/p-GaN heterojunction LEDs under forward bias, while for the reverse bias, blue light was observed. While for the n-ZnO nanorods/p-GaN blue light dominated the emission in both forward and reverse biases. Further, the LEDs exhibited a high sensitivity in responding to UV illumination. The results presented here indicate that doping ZnO nanorods might pave the way to tune the light emission from n-ZnO/p-GaN LEDs.

  20. Antibacterial property of Ag nanoparticle-impregnated N-doped titania films under visible light

    NASA Astrophysics Data System (ADS)

    Wong, Ming-Show; Chen, Chun-Wei; Hsieh, Chia-Chun; Hung, Shih-Che; Sun, Der-Shan; Chang, Hsin-Hou

    2015-07-01

    Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet-visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films.

  1. Antibacterial property of Ag nanoparticle-impregnated N-doped titania films under visible light

    PubMed Central

    Wong, Ming-Show; Chen, Chun-Wei; Hsieh, Chia-Chun; Hung, Shih-Che; Sun, Der-Shan; Chang, Hsin-Hou

    2015-01-01

    Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet–visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films. PMID:26156001

  2. Antibacterial property of Ag nanoparticle-impregnated N-doped titania films under visible light.

    PubMed

    Wong, Ming-Show; Chen, Chun-Wei; Hsieh, Chia-Chun; Hung, Shih-Che; Sun, Der-Shan; Chang, Hsin-Hou

    2015-07-09

    Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet-visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films.

  3. UV light emitting transparent conducting tin-doped indium oxide (ITO) nanowires.

    PubMed

    Gao, J; Chen, R; Li, D H; Jiang, L; Ye, J C; Ma, X C; Chen, X D; Xiong, Q H; Sun, H D; Wu, T

    2011-05-13

    Multifunctional single crystalline tin-doped indium oxide (ITO) nanowires with tuned Sn doping levels are synthesized via a vapor transport method. The Sn concentration in the nanowires can reach 6.4 at.% at a synthesis temperature of 840 °C, significantly exceeding the Sn solubility in ITO bulks grown at comparable temperatures, which we attribute to the unique feature of the vapor-liquid-solid growth. As a promising transparent conducting oxide nanomaterial, layers of these ITO nanowires exhibit a sheet resistance as low as 6.4 Ω/[Symbol: see text] and measurements on individual nanowires give a resistivity of 2.4 × 10(-4) Ω cm with an electron density up to 2.6 × 10(20) cm(-3), while the optical transmittance in the visible regime can reach ∼ 80%. Under the ultraviolet excitation the ITO nanowire samples emit blue light, which can be ascribed to transitions related to defect levels. Furthermore, a room temperature ultraviolet light emission is observed in these ITO nanowires for the first time, and the exciton-related radiative process is identified by using temperature-dependent photoluminescence measurements.

  4. Enhanced visible-light photocatalysis and gas sensor properties of polythiophene supported tin doped titanium nanocomposite

    NASA Astrophysics Data System (ADS)

    Chandra, M. Ravi; Siva Prasada Reddy, P.; Rao, T. Siva; Pammi, S. V. N.; Siva Kumar, K.; Vijay Babu, K.; Kiran Kumar, Ch.; Hemalatha, K. P. J.

    2017-06-01

    The polythiophene supported tin doped titanium nanocomposites (PTh/Sn-TiO2) were synthesized by modified sol-gel process through oxidative polymerization of thiophene. The fourier transform infrared spectroscopy (FT-IR) and UV-Vis diffuse reflectance spectroscopy (UV-DRS) analysis confirms the existence of synergetic interaction between metal oxide and polymer along with extension of absorption edge to visible region. The composites are found to be in spherical form with core-shell structure, which is confirmed by scanning electron spectroscopy (SEM) and transmission electron microscopy (TEM) images, the presence of all respective elements of composite are proven by energy-dispersive X-ray spectroscopy (EDX) analysis. The importance of polythiophene on surface of metal oxide has been were studied as a function of photocatalytic activity for degradation of organic pollutant congo red and gas sensor behavior towards liquid petroleum gas (LPG). All the composites are photocatalytically active and the composite with 1.5 wt% thiophene degrades the pollutant congo red within 120 min when compared to remaining catalysts under visible light irradiation. On the other hand, same composite have shown potential gas sensor properties towards LPG at 300 °C. Considering all the results, it can be noted that polythiophene acts as good sensitizer towards LPG and supporter for the tin doped titania that improve the photocatalytic activity under visible light.

  5. Strengthening TiN diffusion barriers for Cu metallization by lightly doping Al

    NASA Astrophysics Data System (ADS)

    Yang, L. C.; Hsu, C. S.; Chen, G. S.; Fu, C. C.; Zuo, J. M.; Lee, B. Q.

    2005-09-01

    Thin films of Ti1-xAlxN were deposited on (100) Si by ultrahigh-vacuum dual-target reactive sputtering, and the impact of lightly doping Al of x as small as 0.09 on altering the films's microstructure upon thermal annealing, and hence the performance of the films (40nm thick) as diffusion barriers for Cu metallization was evaluated. The results of transmission electron microscopy, Rutherford backscattering spectroscopy, and grazing-incidence x-ray diffraction show that the TiN barrier layer gives the commonly observed voided, columnar grains composed of 5nm sized subgrains. Upon annealing, the subgrains tend to coalesce into 20nm sized equiaxed grains full of crystalline defects, initiating an inward penetration of Cu and a partial dissociation of TiN, transforming themselves, respectively, into pyramidal (or columnar) Cu3Si precipitates and a dendritic Ti5Si3 layer just after 550°C, 10min annealing. However, the lightly doped Al not only overrides the tendency to form intercolumnar voids inherent in sputter deposition by self-shadowing and statistical roughening, but also substantially enhances the microstructural and thermochemical stability, hence significantly improving barrier property, as evidenced from an annealing test at an elevated temperature (600°C) for a prolonged period of 30min.

  6. Optical properties and generation of white light in Dy3+-doped lead phosphate glasses

    NASA Astrophysics Data System (ADS)

    Linganna, K.; Rao, Ch. Srinivasa; Jayasankar, C. K.

    2013-03-01

    Dy3+-doped lead phosphate (PbPKANDy: P2O5+K2O+Al2O3+PbO+Na2O+Dy2O3) glasses were prepared by melt quenching technique and their optical properties have been studied. Judd-Ofelt parameters have been evaluated for 1.0 mol% Dy2O3-doped lead phosphate glass and inturn derived radiative properties for excited luminescent levels of Dy3+ ions. The yellow-to-blue emission intensity ratios and CIE chromaticity coordinates were calculated which have been used to evaluate white light emission as a function of the activator (Dy3+) ion concentration. The observed non-exponential decay nature and quenching of lifetime for higher Dy3+ ion concentration (≥1.0 mol%) have been attributed due to energy transfer of dipole-dipole type between excited and unexcited Dy3+ ions. The PbPKANDy glasses exhibit better luminescence properties which are suitable for generation of white light.

  7. Nitrogen Doped Graphene Nickel Ferrite Magnetic Photocatalyst for the Visible Light Degradation of Methylene Blue.

    PubMed

    Singh, Rajinder; Ladol, Jigmet; Khajuria, Heena; Sheikh, Haq Nawaz

    2017-01-01

    A facile approach has been devised for the preparation of magnetic NiFe2O4 photocatalyst (NiFe2O4-NG) supported on nitrogen doped graphene (NG). The NiFe2O4-NG composite was synthesized by one step hydrothermal method. The nanocomposite catalyst was characterized by Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Ultraviolet-visible spectroscopy (UV-Vis) and Vibrating sample magnetometry (VSM). It is found that the combination of NiFe2O4 nanoparticles with nitrogen-doped graphene sheets converts NiFe2O4 into a good catalyst for methylene blue (MB) dye degradation by irradiation of visible light. The catalytic activity under visible light irradiation is assigned to extensive movement of photogenerated electron from NiFe2O4 to the conduction band of the reduced NG, effectively blocking direct recombination of electrons and holes. The NiFe2O4 nanoparticles alone have efficient magnetic property, so can be used for magnetic separation in the solution without additional magnetic support.

  8. Manufactures and Characterizations of Photodiode Thin Film Barium Strontium Titanate (BST) Doped by Niobium and Iron as Light Sensor

    NASA Astrophysics Data System (ADS)

    Dahrul, Muhammad; Syafutra, Heriyanto; Arif, Ardian; Irzaman, Indro; Nur, Muhammad; Siswadi

    2010-12-01

    Pure Ba0,5Sr0,5TiO3 (BST) thin film, BST doped by niobium (BNST) and BST doped by iron (BFST) have been synthesized on p-type Si (100) substrates using Chemical Solution Deposition (CSD) methods followed by spin coating and annealing techniques. Current-voltage characterizations on these sample result in agreement that all of the BST, BNST, and BFST thin films have photodiode properties. Electrical conductivity values of BST, BNST, and BFST are in the range of conductivity values of semiconductor materials. Niobium or iron doping on the BST samples increase their conductivity value their dielectric constant. This conductivity values may change when a light is exposed on the film surface. Absorbance and reflectance characterizations show that the BST, BNST, and BFST thin films absorb certain range of visible and infrared light. It is convincing that the BST, BNST, and BFST thin films might be used as photodiode light sensor.

  9. Photocatalytic degradation of p,p'-DDT under UV and visible light using interstitial N-doped TiO₂.

    PubMed

    Ananpattarachai, Jirapat; Kajitvichyanukul, Puangrat

    2015-01-01

    1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (or p,p'-DDT) is one of the most persistent pesticides. It is resistant to breakdown in nature and cause the water contamination problem. In this work, a major objective was to demonstrate the application of N-doped TiO2 in degradation and mineralization of the p,p'-DDT under UV and visible light in aqueous solution. The N-doped TiO2 nanopowders were prepared by a simple modified sol-gel procedure using diethanolamine (DEA) as a nitrogen source. The catalyst characteristics were investigated using XRD, SEM, TEM, and XPS. The adsorption and photocatalytic oxidation of p,p'-DDT using the synthesized N-doped TiO2 under UV and visible light were conducted in a batch photocatalytic experiment. The kinetics and p,p'-DDT degradation performance of the N-doped TiO2 were evaluated. Results show that the N-doped TiO2 can degrade p,p'-DDT effectively under both UV and visible lights. The rate constant of the p,p'-DDT degradation under UV light was only 0.0121 min(-1), whereas the rate constant of the p,p'-DDT degradation under visible light was 0.1282 min(-1). Under visible light, the 100% degradation of p,p'-DDT were obtained from N-doped TiO2 catalyst. The reaction rate of p,p'-DDT degradation using N-doped TiO2 under visible light was sixfold higher than that under UV light. According to Langmuir-Hinshelwood model, the adsorption equilibrium constant (K) for the N-doped TiO2 under visible light was 0.03078 L mg(-1), and the apparent reaction rate constant (k) was 1.3941 mg L(-1)-min. Major intermediates detected during the p,p'-DDT degradation were p,p'-DDE, o,p'-DDE, p,p'-DDD and p,p'-DDD. Results from this work can be applied further for the breakdown of p,p'-DDT molecule in the real contaminated water using this technology.

  10. Study of new states in visible light active W, N co-doped TiO{sub 2} photo catalyst

    SciTech Connect

    Sajjad, Ahmed Khan Leghari; Shamaila, Sajjad; Zhang, Jinlong

    2012-11-15

    Highlights: ► Visible light efficient W, N co-doped TiO{sub 2} photo catalysts are prepared by sol–gel. ► Oxygen vacancies are detected in the form of new linkages as N-Ti-O, N-W-O, Ti-O-N and W-O-N. ► W, N co-doped titania has new energy states which narrows the band gap effectively. ► Oxygen vacancies are proved to be the cause for high photo catalytic activity. ► W and N co-doping plays the major role to make the composite thermally stable. -- Abstract: The visible light efficient W, N co-doped TiO{sub 2} photo catalysts are prepared by sol–gel method. New linkages of N, W and O are formed as N-Ti-O, N-W-O, Ti-O-N and W-O-N. Electron paramagnetic resonance illustrates the presence of oxygen vacancies in W, N co-doped TiO{sub 2} acting as trapping agencies for electrons to produce active species. X-ray photoelectron spectroscopy confirms the presence of new energy states. New linkages and oxygen vacancies are proved to be the main cause for the improved photo catalytic performances. W, N co-doped TiO{sub 2} has new energy states which narrow the band gap effectively. W, N co-doped TiO{sub 2} is thermally stable and retains its anatase phase up to 900 °C. 4.5% W, N co-doped TiO{sub 2} showed superior activity for the degradation of Rhodamine B and 2,4-dichlorophenol as compared to pure titania, Degussa P-25, traditional N-doped TiO{sub 2} and pure WO{sub 3}.

  11. Visible light induced electron transfer process over nitrogen doped TiO(2) nanocrystals prepared by oxidation of titanium nitride.

    PubMed

    Wu, Zhongbiao; Dong, Fan; Zhao, Weirong; Guo, Sen

    2008-08-30

    Nitrogen doped TiO(2) nanocrystals with anatase and rutile mixed phases were prepared by incomplete oxidation of titanium nitride at different temperatures. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), core level X-ray photoelectron spectroscopy (CL XPS), valence band X-ray photoelectron spectroscopy (VB XPS), UV-vis diffuse reflectance spectra (UV-vis DRS), and visible light excited photoluminescence (PL). The photocatalytic activity was evaluated for photocatalytic degradation of toluene in gas phase under visible light irradiation. The visible light absorption and photoactivities of these nitrogen doped TiO(2) nanocrystals can be clearly attributed to the change of the additional electronic (N(-)) states above the valence band of TiO(2) modified by N dopant as revealed by the VB XPS and visible light induced PL. A band gap structure model was established to explain the electron transfer process over nitrogen doped TiO(2) nanocrystals under visible light irradiation, which was consistent with the previous theoretical and experimental results. This model can also be applied to understand visible light induced photocatalysis over other nonmetal doped TiO(2).

  12. Synthesis and photocatalytic activity of mesoporous cerium doped TiO{sub 2} as visible light sensitive photocatalyst

    SciTech Connect

    Aman, Noor; Satapathy, P.K.; Mishra, T.; Mahato, M.; Das, N.N.

    2012-02-15

    Graphical abstract: Cerium doped titania having optimum 5 wt% of cerium can decompose methylene blue and reduce selenium (IV) efficiently under visible light. Highlights: Black-Right-Pointing-Pointer Effect of cerium doping on the surface properties and visible light mediated photocatalytic reaction is studied. Black-Right-Pointing-Pointer Cerium doping increases the anatase phase stability, surface area (up to 137 m{sup 2}/g) and visible light absorption. Black-Right-Pointing-Pointer Importance of Ce{sup 3+}/Ce{sup 4+}, oxygen vacancy, surface area and crystallinity is correlated with improved catalytic activity. Black-Right-Pointing-Pointer Material with 5 wt% Ce is found to be most active photocatalyst for methylene blue decomposition and Se (IV) reduction. -- Abstract: Cerium doped titania materials were synthesized varying the cerium concentration from 0 to 10 wt%. Materials are characterised by XRD, TEM, XPS and N{sub 2} adsorption desorption method. Surface area and visible light absorption substantially increases and crystallite size decreases with the increasing cerium content. Cerium doping stabilizes the anatase phase and surface area even at 600 Degree-Sign C calcination. Photocatalytic activity towards methylene blue decomposition and selenium (IV) reduction is found to increase with the cerium content up to 5 wt% and then decreases. Materials calcined at 600 Degree-Sign C shows better activity than that calcined at 400 Degree-Sign C, even though surface area decreases. Anatase crystallinity mostly decides the photocatalytic activity rather than only surface area. It can be concluded that the optimum visible light absorption and oxygen vacancy with 5% cerium doping enhances the photocatalytic activity. In addition photocatalytic performance is found to depend on the presence of Ce{sup 4+}/Ce{sup 3+} rather than only visible light absorption.

  13. Photocatalytic activity of tungsten-doped TiO2 with hydrothermal treatment under blue light irradiation.

    PubMed

    Putta, Thapanan; Lu, Ming-Chun; Anotai, Jin

    2011-09-01

    Tungsten doping and hydrothermal treatment were found to significantly improve the visible-light photoactivity of TiO(2) synthesized by the sol-gel method. It was observed that TiO(2) doped with a 0.5% W:Ti mole ratio and treated with 4 h of hydrothermal curing showed photoactivity under blue light irradiation equal to 74% of the commercial Degussa P-25 under UV irradiation, i.e., 0.01 mM 2-chlorophenol was completely removed in 120 and 90 min, respectively. Light absorptivity and photocatalytic activity under blue light irradiation were not dependent on the crystallite structure of the TiO(2). The oxidation kinetics under blue light irradiation can be effectively explained by the Langmuir-Hinshelwood model with an apparent reaction rate constant and a Langmuir constant of 3.60 × 10(-4) mM min(-1) and 206.53 mM(-1), respectively.

  14. Energy transfer and device performance in phosphorescent dye doped polymer light emitting diodes

    NASA Astrophysics Data System (ADS)

    Noh, Yong-Young; Lee, Chang-Lyoul; Kim, Jang-Joo; Yase, Kiyoshi

    2003-02-01

    Singlet and triplet-triplet energy transfer in phosphorescent dye doped polymer light emitting devices were investigated. Poly(N-vinylcarbazol) and poly[9,9'-di-n-hexyl-2,7-fluorene-alt- 1,4-(2,5-di-n-hexyloxy)phenylene] (PFHP) were selected as the host polymer for the phosphorescent dopants fac-tris(2-phenylpyridine) iridium(III) [Ir(ppy)3] and 2,3,7,8,12,13, 17,18-octaethyl-21H,23H-porphyrin platinum(II) (PtOEP) because of their high triplet energy levels and long phosphorescence lifetimes. In case of PVK film, efficient triplet energy transfers to both PtOEP and Ir(ppy)3 were observed. In contrast, the triplet energy transfer did not occur or was very weak from PFHP to both PtOEP and Ir(ppy)3 although usual requirements for triplet energy transfer were satisfied. Furthermore, the singlet-singlet energy transfer did not take place from PFHP to Ir(ppy)3 in doped films even though the Förster radius is more than 30 Å. However, the blended film of Ir(ppy)3 with PFHP and PMMA showed the green emission from Ir(ppy)3 via singlet energy transfer. In addition, the solution of PFHP and Ir(ppy)3 (8 wt. %) in p-xylene also showed green emission. The blocking of the energy transfers in the phosphorescent dye doped PFHP films is found to be originated from the formation of aggregates which is evident from the microscopic images taken by transmission electron microscope, atomic force microscope, and fluorescence microscope. The formation of aggregates prevents dopant molecules from being in close proximity with host molecules thereby inhibiting energy transfer processes. The phase separation deteriorates the device performance also. Therefore, the chemical compatibility of a dopant with a host polymer as well as conventional requirements for energy transfers must be significantly considered to fabricate efficient phosphorescent dye doped polymer light emitting devices.

  15. Degradation of nitrobenzene using titania photocatalyst co-doped with nitrogen and cerium under visible light illumination.

    PubMed

    Shen, Xiang-Zhong; Liu, Zhi-Cheng; Xie, Shan-Mei; Guo, Jun

    2009-03-15

    A type of nitrogen and cerium co-doped titania photocatalyst, which could degrade nitrobenzene under visible light irradiation, was prepared by the sol-gel route. Titanium isopropoxide, ammonium nitrate, and cerium nitrate were used as the sources of titanium, nitrogen, and cerium, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffusive reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and N(2) adsorption-desorption isotherm were employed to characterize the as-prepared photocatalyst. The degradation of nitrobenzene under visible light illumination was taken as probe reaction to evaluate the photoactivity of the co-doped photocatalyst. The commercial TiO(2) photocatalyst (Degussa P25), which was thought as a high active photocatalyst, was chosen as standard photocatalyst to contrast the photoactivity of the nitrogen and cerium co-doped titania photocatalyst. The results showed that the photocatalytic performance of the nitrogen and cerium co-doped titania was related with the calcination temperature and the component. The nitrogen atoms were incorporated into the crystal of titania and could narrow the band gap energy. The doping cerium atoms existed in the forms of Ce(2)O(3) and dispersed on the surface of TiO(2). The improvement of the photocatalytic activity was ascribed to the synergistic effects of the nitrogen and cerium co-doping.

  16. Visible Light Photocatalysis with Nitrogen-Doped Titanium Dioxide Nanoparticles Prepared by Plasma Assisted Chemical Vapor Deposition

    SciTech Connect

    Buzby,S.; Barakat, M.; Lin, H.; Ni, C.; Rykov, S.; Chen, J.; Shah, S.

    2006-01-01

    Nitrogen-doped TiO{sub 2} nanoparticles were synthesized via plasma assisted metal organic chemical vapor deposition. Nitrogen dopant concentration was varied from 0 to 1.61 at. %. The effect of nitrogen ion doping on visible light photocatalysis has been investigated. Samples were analyzed by various analytical techniques such as x-ray diffraction, transmission electron microscopy, x-ray photoelectron spectroscopy, and near-edge x-ray absorption fine structure. Titanium tetraisopropoxide was used as the titanium precursor, while rf-plasma-decomposed ammonia was used as the source for nitrogen doping. The N-doped TiO{sub 2} nanoparticles were deposited on stainless steel mesh under a flow of Ar and O2 gases at 600 {sup o}C in a tube reactor. The photocatalytic activity of the prepared N-doped TiO{sub 2} samples was tested by the degradation of 2-chlorophenol (2-CP) in an aqueous solution using a visible lamp equipped with an UV filter. The efficiency of photocatalytic oxidation of 2-CP was measured using high performance liquid chromatography. Results obtained revealed the formation of N-doped TiO{sub 2} samples as TiO{sub 2-x}N{sub x}, and a corresponding increase in the visible light photocatalytic activity.

  17. Bismuth-doped ordered mesoporous TiO2: visible-light catalyst for simultaneous degradation of phenol and chromium.

    PubMed

    Sajjad, Shamaila; Leghari, Sajjad A K; Chen, Feng; Zhang, Jinlong

    2010-12-10

    A controllable and reproducible synthesis of highly ordered two-dimensional hexagonal mesoporous, crystalline bismuth-doped TiO(2) nanocomposites with variable Bi ratios is reported here. Analyses by transmission electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy reveal that the well-ordered mesostructure is doped with Bi, which exists as Bi(3+) and Bi((3+x+)). The Bi-doped mesoporous TiO(2) (ms-TiO(2)) samples exhibit improved photocatalytic activities for simultaneous phenol oxidation and chromium reduction in aqueous suspension under visible and UV light over the pure ms-TiO(2), P-25, and conventional Bi-doped titania. The high catalytic activity is due to both the unique structural characteristics and the Bi doping. This new material extends the spectral response from UV to the visible region, and reduces electron-hole recombination, which renders the 2.0% Bi-doped ms-TiO(2) photocatalyst highly responsive to visible light.

  18. Narrow band gap and visible light-driven photocatalysis of V-doped Bi6Mo2O15 nanoparticles

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Qin, Chuanxiang; Huang, Yanlin; Wang, Yaorong; Qin, Lin; Seo, Hyo Jin

    2017-02-01

    Pure and V5+-doped Bi6Mo2O15 (3Bi2O3·2MoO3) photocatalysts were synthesized through electrospinning, followed by low-temperature heat treatment. The samples developed into nanoparticles with an average size of approximately 50 nm. The crystalline phases were verified via X-ray powder diffraction measurements (XRD). The surface properties of the photocatalysts were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses. The UV-vis spectra showed that V doping in Bi6Mo2O15 shifted the optical absorption from the UV region to the visible-light wavelength region. The energy of the band gap of Bi6Mo2O15 was reduced by V doping in the lattices. The photocatalytic activities of the pure and V-doped Bi6Mo2O15 were tested through photodegradation of rhodamine B (RhB) dye solutions under visible light irradiation. Results showed that 20 mol% V-doped Bi6Mo2O15 achieved efficient photocatalytic ability. RhB could be degraded by V-doped Bi6Mo2O15 in 2 h. The photocatalytic activities and mechanisms were discussed according to the characteristics of the crystal structure and the results of EIS and XPS measurements.

  19. Structural transformation of Sm3+ doped BiVO4 with high photocatalytic activity under simulated sun-light

    NASA Astrophysics Data System (ADS)

    Luo, Yangyang; Tan, Guoqiang; Dong, Guohua; Zhang, Lili; Huang, Jing; Yang, Wei; Zhao, Chengcheng; Ren, Huijun

    2015-01-01

    A series of Sm3+ doped BiVO4 photocatalysts with high photocatalytic efficiency were successfully synthesized by a microwave hydrothermal method. The effects of Sm3+ doping on the crystal structure, morphology, optical absorption and photocatalytic activity were investigated systematically. From the structural characterization of photocatalysts, the incorporation of Sm3+ into BiVO4 could induce the stabilization of tetragonal phase. Meanwhile, the morphology and grain size show an obvious change with doping Sm3+ ions. The Sm3+ doped BiVO4 with the optical absorption in UV-light range would accelerate more photogenerated electron-hole pairs, which is in favor of the improvement of photocatalytic activity. The best photocatalytic performance is obtained for the 6at% Sm3+ doped BiVO4, of which the degradation rate of Rhodamine B (RhB) can reach to 96% after 120 min simulated sun-light irradiation. Moreover, the photocurrent results indicate that the obviously enhanced photocatalytic activity of Sm3+ doped BiVO4 can be attributed to the efficient separation of photogenerated electron-hole pairs.

  20. Workfunction-tunable, N-doped reduced graphene transparent electrodes for high-performance polymer light-emitting diodes.

    PubMed

    Hwang, Jin Ok; Park, Ji Sun; Choi, Dong Sung; Kim, Ju Young; Lee, Sun Hwa; Lee, Kyung Eun; Kim, Yong-Hyun; Song, Myoung Hoon; Yoo, Seunghyup; Kim, Sang Ouk

    2012-01-24

    Graphene is a promising candidate to complement brittle and expensive transparent conducting oxides. Nevertheless, previous research efforts have paid little attention to reduced graphene, which can be of great benefit due to low-cost solution processing without substrate transfer. Here we demonstrate workfunction-tunable, highly conductive, N-doped reduced graphene film, which is obtainable from the spin-casting of graphene oxide dispersion and can be successfully employed as a transparent cathode for high-performance polymer light-emitting diodes (PLEDs) as an alternative to fluorine-doped tin oxide (FTO). The sheet resistance of N-doped reduced graphene attained 300 Ω/□ at 80% transmittance, one of the lowest values ever reported from the reduction of graphene oxide films. The optimal doping of quaternary nitrogen and the effective removal of oxygen functionalities via sequential hydrazine treatment and thermal reduction accomplished the low resistance. The PLEDs employing N-doped reduced graphene cathodes exhibited a maximum electroluminescence efficiency higher than those of FTO-based devices (4.0 cd/A for FTO and 7.0 cd/A for N-doped graphene at 17,000 cd/m(2)). The reduced barrier for electron injection from a workfunction-tunable, N-doped reduced graphene cathode offered this remarkable device performance.

  1. Phosphorus Doping in Si Nanocrystals/SiO2 msultilayers and Light Emission with Wavelength compatible for Optical Telecommunication.

    PubMed

    Lu, Peng; Mu, Weiwei; Xu, Jun; Zhang, Xiaowei; Zhang, Wenping; Li, Wei; Xu, Ling; Chen, Kunji

    2016-03-09

    Doping in semiconductors is a fundamental issue for developing high performance devices. However, the doping behavior in Si nanocrystals (Si NCs) has not been fully understood so far. In the present work, P-doped Si NCs/SiO2 multilayers are fabricated. As revealed by XPS and ESR measurements, P dopants will preferentially passivate the surface states of Si NCs. Meanwhile, low temperature ESR spectra indicate that some P dopants are incorporated into Si NCs substitutionally and the incorporated P impurities increase with the P doping concentration or annealing temperature increasing. Furthermore, a kind of defect states will be generated with high doping concentration or annealing temperature due to the damage of Si crystalline lattice. More interestingly, the incorporated P dopants can generate deep levels in the ultra-small sized (~2 nm) Si NCs, which will cause a new subband light emission with the wavelength compatible with the requirement of the optical telecommunication. The studies of P-doped Si NCs/SiO2 multilayers suggest that P doping plays an important role in the electronic structures and optoelectronic characteristics of Si NCs.

  2. Investigation of p-type depletion doping for InGaN/GaN-based light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Zhang, Yiping; Zhang, Zi-Hui; Tan, Swee Tiam; Hernandez-Martinez, Pedro Ludwig; Zhu, Binbin; Lu, Shunpeng; Kang, Xue Jun; Sun, Xiao Wei; Demir, Hilmi Volkan

    2017-01-01

    Due to the limitation of the hole injection, p-type doping is essential to improve the performance of InGaN/GaN multiple quantum well light-emitting diodes (LEDs). In this work, we propose and show a depletion-region Mg-doping method. Here we systematically analyze the effectiveness of different Mg-doping profiles ranging from the electron blocking layer to the active region. Numerical computations show that the Mg-doping decreases the valence band barrier for holes and thus enhances the hole transportation. The proposed depletion-region Mg-doping approach also increases the barrier height for electrons, which leads to a reduced electron overflow, while increasing the hole concentration in the p-GaN layer. Experimentally measured external quantum efficiency indicates that Mg-doping position is vitally important. The doping in or adjacent to the quantum well degrades the LED performance due to Mg diffusion, increasing the corresponding nonradiative recombination, which is well supported by the measured carrier lifetimes. The experimental results are well numerically reproduced by modifying the nonradiative recombination lifetimes, which further validate the effectiveness of our approach.

  3. Phosphorus Doping in Si Nanocrystals/SiO2 msultilayers and Light Emission with Wavelength compatible for Optical Telecommunication

    PubMed Central

    Lu, Peng; Mu, Weiwei; Xu, Jun; Zhang, Xiaowei; Zhang, Wenping; Li, Wei; Xu, Ling; Chen, Kunji

    2016-01-01

    Doping in semiconductors is a fundamental issue for developing high performance devices. However, the doping behavior in Si nanocrystals (Si NCs) has not been fully understood so far. In the present work, P-doped Si NCs/SiO2 multilayers are fabricated. As revealed by XPS and ESR measurements, P dopants will preferentially passivate the surface states of Si NCs. Meanwhile, low temperature ESR spectra indicate that some P dopants are incorporated into Si NCs substitutionally and the incorporated P impurities increase with the P doping concentration or annealing temperature increasing. Furthermore, a kind of defect states will be generated with high doping concentration or annealing temperature due to the damage of Si crystalline lattice. More interestingly, the incorporated P dopants can generate deep levels in the ultra-small sized (~2 nm) Si NCs, which will cause a new subband light emission with the wavelength compatible with the requirement of the optical telecommunication. The studies of P-doped Si NCs/SiO2 multilayers suggest that P doping plays an important role in the electronic structures and optoelectronic characteristics of Si NCs. PMID:26956425

  4. White light emitting Ho{sup 3+}-doped CdS nanocrystal ingrained glass nanocomposites

    SciTech Connect

    Dey, Chirantan; Karmakar, Basudeb; Goswami, Madhumita

    2015-02-23

    We report the generation of white light from Ho{sup 3+} ion doped CdS nanocrystal ingrained borosilicate glass nanocomposites prepared by the conventional melt-quench method. Near visible 405 nm diode laser excited white light emission is produced by tuning the blue emission from the Ho{sup 3+} ions, green band edge, and orange-red surface-state emissions of the nanocrystalline CdS, which are further controlled by the size of the nanocrystals. The absorption and emission spectra evidenced the excitation of Ho{sup 3+} ions by absorption of photons emitted by the CdS nanocrystals. The high color rendering index (CRI = 84–89) and befitting chromaticity coordinates (x = 0.308–0.309, y = 0.326–0.338) of white light emission, near visible harmless excitation wavelength (405 nm), and high absorbance values at excitation wavelength point out that these glass nanocomposites may serve as a prominent candidate for resin free high power white light emitting diodes.

  5. Visible-Light-Induced Bactericidal Activity of Titanium Dioxide Co-doped with Nitrogen and Silver

    PubMed Central

    Wu, Pinggui; Xie, Rongcai; Imlay, Kari; Shang, Jian-Ku

    2011-01-01

    Titanium dioxide nanoparticles co-doped with nitrogen and silver (Ag2O/TiON) were synthesized by the sol-gel process and found to be an effective visible light driven photocatalyst. The catalyst showed strong bactericidal activity against Escherichia coli (E. coli) under visible light irradiation (λ> 400 nm). In x-ray photoelectron spectroscopy and x-ray diffraction characterization of the samples, the as-added Ag species mainly exist as Ag2O. Spin trapping EPR study showed Ag addition greatly enhanced the production of hydroxyl radicals (•OH) under visible light irradiation. The results indicate that the Ag2O species trapped eCB− in the process of Ag2O/TiON photocatalytic reaction, thus inhibiting the recombination of eCB− and hVB+ in agreement with the stronger photocatalytic bactericidal activity of Ag2O/TiON. The killing mechanism of Ag2O/TiON under visible light irradiation is shown to be related to oxidative damages in the forms of cell wall thinning and cell disconfiguration. PMID:20726520

  6. Photodegradation of aniline by goethite doped with boron under ultraviolet and visible light irradiation

    SciTech Connect

    Liu, Guanglong; Liao, Shuijiao; Zhu, Duanwei; Liu, Linghua; Cheng, Dongsheng; Zhou, Huaidong

    2011-08-15

    Highlights: {yields} Goethite modified by boron was prepared by sol-gel method in presence of boron acid at the low temperature. {yields} B-goethite has slight red shift in the band gap transition beside their stronger light absorption compared with pristine goethite. {yields} The results showed that semiconductor photocatalytic reaction mechanism should exist in the process of aniline degradation with goethite and B-goethite as photocatalyst. -- Abstract: In the present study, goethite and goethite doped with boron (B-goethite) were employed to detect the presence or absence of semiconductor photocatalytic reaction mechanism in the reaction systems. B-goethite was prepared by sol-gel method in presence of boron acid in order to improve its photocatalystic efficiency under the ultraviolet and visible light irradiation. The optical properties of goethite and B-goethite were characterized by ultraviolet and visible absorption spectra and the result indicated that B-goethite has slight red shift in the band gap transition beside their stronger light absorption compared with pristine goethite. Degradation of aniline was investigated in presence of goethite and B-goethite in aqueous solution. It was found that the B-goethite photocatalyst exhibited enhanced ultraviolet and visible light photocatalytic activity in degradation of aniline compared with the pristine goethite. The photocatalytic degradation mechanism of B-goethite was discussed.

  7. Effect of ultraviolet light exposure to boron doped hydrogenated amorphous silicon oxide thin film

    NASA Astrophysics Data System (ADS)

    Baek, Seungsin; Iftiquar, S. M.; Jang, Juyeon; Lee, Sunhwa; Kim, Minbum; Jung, Junhee; Park, Hyeongsik; Park, Jinjoo; Kim, Youngkuk; Shin, Chonghoon; Lee, Youn-Jung; Yi, Junsin

    2012-11-01

    We have investigated the effect of ultraviolet (UV) light exposure to boron doped (p-type) hydrogenated amorphous silicon oxide (p-a-SiO:H) thin semiconductor films by measuring changes in its structural, electrical and optical properties. After a 50 h of UV light soaking (LS) of the films, that have 1.2, 6.9, 15.2, 25.3 at.% oxygen content (C(O)) and optical gap (E04) of 1.897, 2.080, 2.146 and 2.033 eV, show a relative increase in the C(O) by 28.0%, 9.8%, 2.0%, 3.1%, a relative increase in the Urbach energy (Eu) by 42%, 24%, 8%, 0%, decrease in the E04 by 66, 2, 12, 19 meV and the gap state defect density (Nd) show an increase by 6.5%, 3.4%, 0.7%, 0.1%. At higher oxygen content the observed UV light induced degradation (LID) is relatively less than that for films with lower oxygen content, indicating that higher oxides face less changes under the UV light.

  8. Tunable light filtering by a Bragg mirror/heavily doped semiconducting nanocrystal composite.

    PubMed

    Kriegel, Ilka; Scotognella, Francesco

    2015-01-01

    Tunable light filters are critical components for many optical applications in which light in-coupling, out-coupling or rejection is crucial, such as lasing, sensing, photovoltaics and information and communication technology. For this purpose, Bragg mirrors (band-pass filters with high reflectivity) represent good candidates. However, their optical characteristics are determined during the fabrication stage. Heavily doped semiconductor nanocrystals (NCs), on the other hand, deliver a high degree of optical tunability through the active modulation of their carrier density, ultimately influencing their plasmonic absorption properties. Here, we propose the design of an actively tunable light filter composed of a Bragg mirror and a layer of plasmonic semiconductor NCs. We demonstrate that the filtering properties of the coupled device can be tuned to cover a wide range of frequencies from the visible to the near infrared (vis-NIR) spectral region when employing varying carrier densities. As the tunable component, we implemented a dispersion of copper selenide (Cu2-xSe) NCs and a film of indium tin oxide (ITO) NCs, which are known to show optical tunablility with chemical or electrochemical treatments. We utilized the Mie theory to describe the carrier-dependent plasmonic properties of the Cu2-x Se NC dispersion and the effective medium theory to describe the optical characteristics of the ITO film. The transmission properties of the Bragg mirror have been modelled with the transfer matrix method. We foresee ease of experimental realization of the coupled device, where filtering modulation is achieved upon chemical and electrochemical post-fabrication treatment of the heavily doped semiconductor NC component, eventually resulting in tunable transmission properties of the coupled device.

  9. Tunable light filtering by a Bragg mirror/heavily doped semiconducting nanocrystal composite

    PubMed Central

    Kriegel, Ilka

    2015-01-01

    Summary Tunable light filters are critical components for many optical applications in which light in-coupling, out-coupling or rejection is crucial, such as lasing, sensing, photovoltaics and information and communication technology. For this purpose, Bragg mirrors (band-pass filters with high reflectivity) represent good candidates. However, their optical characteristics are determined during the fabrication stage. Heavily doped semiconductor nanocrystals (NCs), on the other hand, deliver a high degree of optical tunability through the active modulation of their carrier density, ultimately influencing their plasmonic absorption properties. Here, we propose the design of an actively tunable light filter composed of a Bragg mirror and a layer of plasmonic semiconductor NCs. We demonstrate that the filtering properties of the coupled device can be tuned to cover a wide range of frequencies from the visible to the near infrared (vis–NIR) spectral region when employing varying carrier densities. As the tunable component, we implemented a dispersion of copper selenide (Cu2−xSe) NCs and a film of indium tin oxide (ITO) NCs, which are known to show optical tunablility with chemical or electrochemical treatments. We utilized the Mie theory to describe the carrier-dependent plasmonic properties of the Cu2−x Se NC dispersion and the effective medium theory to describe the optical characteristics of the ITO film. The transmission properties of the Bragg mirror have been modelled with the transfer matrix method. We foresee ease of experimental realization of the coupled device, where filtering modulation is achieved upon chemical and electrochemical post-fabrication treatment of the heavily doped semiconductor NC component, eventually resulting in tunable transmission properties of the coupled device. PMID:25671163

  10. Comparison of dye doping and ultrathin emissive layer in white organic light-emitting devices with dual emissive layers

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Qi, Yige; Yu, Junsheng

    2014-09-01

    White organic light-emitting devices (WOLEDs) with combined doping emissive layer (EML) and ultrathin EML have been fabricated to investigate the effect of each EML on the electroluminescent (EL) performance of the WOLEDs. Through tailoring doping concentration of bis[(4,6-difluorophenyl)-pyridinato-N,C2'](picolinate) iridium(III) (FIrpic) and thickness of ultrathin bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2'] iridium (acetylacetonate) [(tbt)2Ir(acac)] EML, it is found that the change in the doping ratio of FIrpic significantly influenced the EL efficiencies and spectra, while the alteration of ultrathin EML thickness had much milder effect on the EL performance. The results indicated that ultrathin EML is in favor of reproducibility in mass production compared with doping method.

  11. Black and yellow anatase titania formed by (H,N)-doping: strong visible-light absorption and enhanced visible-light photocatalysis.

    PubMed

    Wei, Shunhang; Wu, Rong; Jian, Jikang; Chen, Fengjuan; Sun, Yanfei

    2015-01-28

    Black and yellow anatase TiO2 doped with hydrogen and nitrogen elements annealed under a N2/Ar/air atmosphere are produced. More interestingly, one kind of black TiO2 has excellent performance for degradation of methylene blue under visible-light irradiation but photodegradation of the other is quite limited.

  12. High visible light photocatalytic property of Co2+-doped TiO2 nanoparticles with mixed phases

    NASA Astrophysics Data System (ADS)

    Zhao, Cong; Shu, Xin; Zhu, Da-chuan; Wei, Shang-hai; Wang, Yu-xin; Tu, Ming-jing; Gao, Wei

    2015-12-01

    Mixed phases Co2+-doped TiO2 nanoparticles have been prepared by a novel method combined with sol-gel and hydrothermal methods. The section of sol-gel method, sol, provides an unstable colloidal reaction system for the next reaction process. The hydrothermal method is to treat the above reaction system to prepare undoped and doped samples. The as-prepared samples have been characterized by XRD, SEM, TEM, HRTEM and UV-vis spectroscopy. The results show that the as-prepared samples contain three titania polymorphs: brookite, rutile and anatase phases. These titania polymorphs probably form polymorph-junctions that can extend the lifetime of photogenerated electron-hole pairs. The photocatalytic activity has been evaluated by the photocatalytic degradation of Rhodamine B in air under visible-light irradiation. The degradation results indicate that the photocatalytic activity of as-prepared samples is higher than that of Degussa P25, especially the doped sample. This is ascribed to the fact that the phases with smaller band gap can enhance visible-light photocatalytic activity, the polymorph-junctions effectively extend the photoelectron lifetime and the nano size effect and Co-doping induce the shift of the absorption edge into the visible-light region. Furthermore, the XRD, SEM, and TEM data indicate that Co2+-doping results in the decrease of particle size.

  13. TiO2 nanopowder co-doped with iodine and boron to enhance visible-light photocatalytic activity.

    PubMed

    Ding, Jianqiang; Yuan, Yali; Xu, Jinsheng; Deng, Jian; Guo, Jianbo

    2009-10-01

    An iodine and boron co-doped TiO2 photocatalyst was prepared by the hydrolyzation-precipitation method. X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), and X-ray photoelectron spectroscopy (XPS) were applied to characterize the crystalline structure, light absorbing ability, and the chemical state of iodine and boron in the photocatalysts. The results of photocatalytic degradation of methyl orange demonstrated that the I-B-TiO2 catalyst prepared at 400 degrees C for 3 h exhibited the highest photocatalytic activity with a methyl orange degradation ratio of 61% under visible-light (lambda > or = 420 nm) irradiation for 120 min. The characterization results revealed that I-B-TiO2 is in conformity with the anatase TiO2 and that the doping of iodine and boron ions could efficiently inhibit the grain growth. Doped iodine was present in the multivalent forms of 17+, I- and I5+. Doped boron was present as B3+ in an as-prepared sample, forming a possible chemical environment such as B-O-Ti. Overall, the doping of I and B enhanced the ability of TiO2 to absorb visible-light, and it was observed that the photocatalytic activity of I-B-TiO2 was enhanced by the synergistic effect of I and B.

  14. Narrow-linewidth red-emission Eu3+-doped TiO2 spheres for light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Zhu, Peifen; Zhu, Hongyang; Qin, Weiping; Dantas, Breno H.; Sun, Wei; Tan, Chee-Keong; Tansu, Nelson

    2016-03-01

    In this work, the amorphous Eu3+-doped TiO2 spheres were synthesized by low cost mixed-solvent method, while the anatase and rutile spheres can be obtained by annealing the as-synthesized amorphous TiO2 spheres at elevated temperatures. The optical properties of Eu3+-doped TiO2 spheres were also investigated, and strong red emission (centered at 610 nm) with narrow line-width of 30 nm was observed under 465 nm or 394 nm excitations for the Eu3+-doped anatase TiO2 spheres. Our findings indicate the potential of using Eu3+-doped TiO2 spheres to achieve red emission with InGaN blue light emitting diodes (LEDs). Owing to the high light extraction efficiency in the GaN-based LEDs using anatase TiO2 spheres as demonstrated in our previous works, this work shows the strong potential of Eu3+-doped TiO2 spheres as the red phosphor material for high efficiency GaN-based white light-emitting diode.

  15. Slow and fast light via two-wave mixing in the rare-earth doped optical fibers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Stepanov, Serguei I.; Plata Sánchez, Marcos; Hernández, Eliseo

    2017-02-01

    Dynamic population Bragg gratings can be recorded in the rare-earth-doped (e.g. doped with erbium or ytterbium) optical fibers with mWatt-scale cw laser power. Two-wave mixing (TWM) via such gratings is utilized in single-frequency fiber lasers and in adaptive interferometric fiber sensors with automatic stabilization of the operation point. Slow and fast light propagation can also be observed in the vicinity of narrow ( 20-200Hz) spectral profile of stationary no-degenerate TWM. In particular, slow light propagation is observed for the purely amplitude grating, recorded in the erbium-doped fiber in spectral range 1510-1550nm. In its turn, in ytterbium-doped fibers at 1064nm (or in erbium-doped fiber at the wavelength below 1500nm) the dynamic grating has significant contribution of the phase component, the TWM profile has essentially asymmetric form, and both slow and fast (superluminal) light propagation is possible at different frequency off-sets between the counter-propagating interacting waves.

  16. Photocatalytic degradation of Orange G on nitrogen-doped TiO2 catalysts under visible light and sunlight irradiation.

    PubMed

    Sun, Jianhui; Qiao, Liping; Sun, Shengpeng; Wang, Guoliang

    2008-06-30

    In this paper, the degradation of an azo dye Orange G (OG) on nitrogen-doped TiO2 photocatalysts has been investigated under visible light and sunlight irradiation. Under visible light irradiation, the doped TiO2 nanocatalysts demonstrated higher activity than the commercial Dugussa P25 TiO2, allowing more efficient utilization of solar light, while under sunlight, P25 showed higher photocatalytic activity. According to the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis spectra analyses, it was found that both the nanosized anatase structure and the appearance of new absorption band in the visible region caused by nitrogen doping were responsible for the significant enhancement of OG degradation under visible light. In addition, the photosensitized oxidation mechanism originated from OG itself was also considered contributing to the higher visible-light-induced degradation efficiency. The effect of the initial pH of the solution and the dosage of hydrogen peroxide under different light sources was also investigated. Under visible light and sunlight, the optimal solution pH was both 2.0, while the optimal dosage of H2O2 was 5.0 and 15.0 mmol/l, respectively.

  17. Photocatalytic degradation of methylene blue dye under visible light over Cr doped strontium titanate (SrTiO3) nanoparticles.

    PubMed

    Qazi, Inamur Rahman; Lee, Woo-Jin; Lee, Hyun-Cheol; Hassan, Mallick Shamshi; Yang, O-Bong

    2010-05-01

    Strontium titanate (SrTiO3) and chromium doped SrTiO3 (Cr/SrTiO3) were prepared by modified sol-gel method with the citric acid as a chelating agent in the ethylene glycol solution for the effective photodegradation of methylene blue dye under visible light irradiation. The synthesized doped and un-doped SrTiO3 nanoparticles were structurally characterized and their photoresponse performances for the efficient degradation of methylene blue dye have been demonstrated. After introducing the Cr on SrTiO3, UV-Vis absorption was appeared the red-shift at 566 nm from 392 nm as compare with bare SrTiO3. The photocatalytic degradation activity of Cr/SrTiO3 was significantly improved to 60% degradation of methylene blue in 3 h under visible light, which is approximately 5 times higher than that of the bare SrTiO3.

  18. Bactericidal activity and mechanism of Ti-doped BiOI microspheres under visible light irradiation.

    PubMed

    Liang, Jialiang; Deng, Jun; Li, Mian; Xu, Tongyan; Tong, Meiping

    2016-11-01

    Ti doped BiOI microspheres were successfully synthesized through a solvothermal method. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectra (DRS) spectroscopy, respectively. The as-synthesized microspheres had 3D hierarchical structures, and the morphologies and visible-light-driven (VLD) disinfection performances were found to be determined by the amount of loaded Ti. The incorporation of Ti in the lattice of BiOI broadened the band gap of BiOI and enhanced the VLD disinfection activity. Ti doped BiOI microspheres with the optimal Ti content exhibited excellent antibacterial performances against both representative Gram-negative and Gram-positive strains, which completely inactivated 3.0×10(7)CFUmL(-1)E. coli in 24min and 3.0×10(6)CFU mL(-1)S. aureus in 45min, respectively. Active species including h(+), e(-), O2(-) and H2O2 were found to play important roles in disinfection system. Moreover, the damage of cell membrane and emission of cytoplasm directly led to the inactivation.

  19. Manipulation and control of the interfacial polarization in organic light-emitting diodes by dipolar doping

    NASA Astrophysics Data System (ADS)

    Jäger, Lars; Schmidt, Tobias D.; Brütting, Wolfgang

    2016-09-01

    Most of the commonly used electron transporting materials in organic light-emitting diodes exhibit interfacial polarization resulting from partially aligned permanent dipole moments of the molecules. This property modifies the internal electric field distribution of the device and therefore enables an earlier flat band condition for the hole transporting side, leading to improved charge carrier injection. Recently, this phenomenon was studied with regard to different materials and degradation effects, however, so far the influence of dilution has not been investigated. In this paper we focus on dipolar doping of the hole transporting material 4,4-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl (NPB) with the polar electron transporting material tris-(8-hydroxyquinolate) aluminum (Alq3). Impedance spectroscopy reveals that changes of the hole injection voltage do not scale in a simple linear fashion with the effective thickness of the doped layer. In fact, the measured interfacial polarization reaches a maximum value for a 1:1 blend. Taking the permanent dipole moment of Alq3 into account, an increasing degree of dipole alignment is found for decreasing Alq3 concentration. This observation can be explained by the competition between dipole-dipole interactions leading to dimerization and the driving force for vertical orientation of Alq3 dipoles at the surface of the NPB layer.

  20. Degradation of gaseous formaldehyde via visible light photocatalysis using multi-element doped titania nanoparticles.

    PubMed

    Laciste, Maricris T; de Luna, Mark Daniel G; Tolosa, Nolan C; Lu, Ming-Chun

    2017-09-01

    This study developed a modified titanium dioxide photocatalyst doped with multi-element synthesized via sol-gel process to productize a novel photocatalyst. The study includes degradation of gaseous formaldehyde under visible light using the synthesized novel titanium dioxide photocatalyst. Varying molar ratios from 0 to 2 percent (%mole in titanium dioxide) of ammonium fluoride, silver nitrate and sodium tungstate as dopant precursors for nitrogen, fluorine, silver and tungsten were used. Photodegradation of gaseous formaldehyde was examined on glass tubular reactors illuminated with blue light emitting diodes (LEDs) using immobilized photocatalyst. The photocatalytic yield is analyzed based on the photocatalyst surface chemical properties via X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) Spectrophotometry, Brunauer-Emmett-Teller (BET) and X-ray Diffraction (XRD) characterization results. The applied modifications enhanced the visible light capability of the catalyst in comparison to the undoped catalyst and commercially available Degussa P-25, such that it photocatalytically degrades 88.1% of formaldehyde in 120 min. Synthesized titanium dioxide photocatalyst exhibits a unique spin orbital at 532.07 eV and 533.27 eV that came from the hybridization of unoccupied Ti d(t2g) levels. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Synthesis of N-doped TiO2 Using Guanidine Nitrate: An Excellent Visible Light Photocatalyst

    EPA Science Inventory

    An excellent visible light active nitrogen-rich TiO2 photocatalyst have been synthesized by using guanidine nitrate as the doping material. The catalytic efficiency of the catalyst has been demonstrated by the decomposition of the dye, methyl orange (MO), and the pollutant, 2,4 d...

  2. Synthesis of N-doped TiO2 Using Guanidine Nitrate: An Excellent Visible Light Photocatalyst

    EPA Science Inventory

    An excellent visible light active nitrogen-rich TiO2 photocatalyst have been synthesized by using guanidine nitrate as the doping material. The catalytic efficiency of the catalyst has been demonstrated by the decomposition of the dye, methyl orange (MO), and the pollutant, 2,4 d...

  3. Photoelectrocatalytic properties of nitrogen doped TiO2/Ti photoelectrode prepared by plasma based ion implantation under visible light.

    PubMed

    Han, Lei; Xin, Yanjun; Liu, Huiling; Ma, Xinxin; Tang, Guangze

    2010-03-15

    Nitrogen doped TiO(2)/Ti photoelectrodes were prepared by a sequence of anodization and plasma based ion implantation (PBII). The properties of this photoelectrode were characterized by scanning electronic microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS), Ultra violet/visible light diffuse reflectance spectra (UV/vis/DRS), surface photovoltage (SPV), etc. Photoelectrocatalytic (PEC) performance of N-doped TiO(2)/Ti photoelectrode was tested under visible light irradiation. Their photocatalytic activity was evaluated by degradation of Rhodamine B (Rh.B). The results of XPS showed that nitrogen element was in form of three species, i.e. beta-N, molecular gamma-N and O-Ti-N, which existed in the lattices of TiO(2) and gaps between molecules. The results of UV/vis/DRS spectra and SPV revealed that proper doping of nitrogen could expand the response of photoelectrodes towards visible light and diminish the recombination of photo-generated holes and electrons, respectively. The photoelectrocatalytic activity of N-doped TiO(2)/Ti photoelectrodes was superior to those of undoped one under visible light region irradiation.

  4. Kinetics stabilized doping: computational optimization of carbon-doped anatase TiO2 for visible-light driven water splitting.

    PubMed

    Sun, Yi-Yang; Zhang, Shengbai

    2016-01-28

    Using density functional theory calculation we investigate the carbon doping of anatase TiO2, a technique widely studied for visible-light driven water splitting. By a detailed analysis of the thermodynamics of C defects in TiO2, we show that any significant concentration of C dopants in the TiO2 lattice must be a result of non-equilibrium doping, which emphasizes the importance of kinetics stabilized C defects. Based on the band gaps calculated using hybrid density functionals, we exclude the possibility of C occupying Ti lattice sites or interstitial sites to enhance visible-light absorption of TiO2, as extensively discussed in the literature. Also, the recently proposed defect with a CO species occupying two O sites yields a too small band gap for water splitting. Two defects that can effectively reduce the band gap for the water splitting application are identified to be: (1) the CO-VO complex, i.e., a C substituting for O (CO) paired with an O vacancy (VO) and (2) the (C2)2O complex with a C dimer (C2) occupying two neighboring O vacancies. Compared with the CO-VO complex, (C2)2O exhibits strong binding (greater than 2.5 eV) between the two C atoms, which could significantly enhance its kinetic stability to survive from high temperature annealing. With a reduced band gap of about 1.4 eV, carbon dimers could be ideal for kinetic doping of anatase TiO2 to enhance its visible-light activity in photocatalytic reactions. Molecular doping using C2H2 or C2H4 as C precursors has been proposed to introduce the carbon dimers into TiO2.

  5. Effect of carrier doping on the formation and collapse of magnetic polarons in lightly hole-doped La1-xSrxCoO3

    SciTech Connect

    Podlesnyak, Andrey A; Ehlers, Georg; Frontzek, Matthias D; Sefat, A. S.; Furrer, Albert; Straessle, Thierry; Pomjakushina, Ekaterina; Conder, Kazimierz; Demmel, F.; Khomskii, D. I.

    2011-01-01

    We investigate the doping dependence of the nanoscale electronic and magnetic inhomogeneities in the hole-doping range 0.002 < x < 0.1 of cobalt based perovskites, La{sub 1-x}Sr{sub x}CoO{sub 3}. Using single-crystal inelastic neutron scattering and magnetization measurements we show that the lightly doped system exhibits magnetoelectronic phase separation in the form of spin-state polarons. Higher hole doping leads to a decay of spin-state polarons in favor of larger scale magnetic clusters, due to competing ferromagnetic correlations of Co{sup 3+} ions which are formed by neighboring polarons. The present data give evidence for two regimes of magnetoelectronic phase separation in this system: (i) x {approx}< 0.05, dominated by ferromagnetic intrapolaron interactions, and (ii) x {approx}> 0.05, dominated by Co{sup 3+}-Co{sup 3+} intracluster interactions. Our conclusions are in good agreement with a recently proposed model of the phase separation in cobalt perovskites.

  6. Synergistic effect on the visible light activity of Ti3+ doped TiO2 nanorods/boron doped graphene composite

    PubMed Central

    Xing, Mingyang; Li, Xiao; Zhang, Jinlong

    2014-01-01

    TiO2/graphene (TiO2-x/GR) composites, which are Ti3+ self-doped TiO2 nanorods decorated on boron doped graphene sheets, were synthesized via a simple one-step hydrothermal method using low-cost NaBH4 as both a reducing agent and a boron dopant on graphene. The resulting TiO2 nanorods were about 200 nm in length with exposed (100) and (010) facets. The samples were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy, X-band electron paramagnetic resonance (EPR), X-ray photoelectron spectra (XPS), transmission electron microscope (TEM), Raman, and Fourier-transform infrared spectroscopy (FTIR). The XRD results suggest that the prepared samples have an anatase crystalline structure. All of the composites tested exhibited improved photocatalytic activities as measured by the degradation of methylene blue and phenol under visible light irradiation. This improvement was attributed to the synergistic effect of Ti3+ self-doping on TiO2 nanorods and boron doping on graphene. PMID:24974890

  7. Synergistic effect on the visible light activity of Ti3+ doped TiO2 nanorods/boron doped graphene composite.

    PubMed

    Xing, Mingyang; Li, Xiao; Zhang, Jinlong

    2014-06-30

    TiO2/graphene (TiO2-x/GR) composites, which are Ti(3+) self-doped TiO2 nanorods decorated on boron doped graphene sheets, were synthesized via a simple one-step hydrothermal method using low-cost NaBH4 as both a reducing agent and a boron dopant on graphene. The resulting TiO2 nanorods were about 200 nm in length with exposed (100) and (010) facets. The samples were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy, X-band electron paramagnetic resonance (EPR), X-ray photoelectron spectra (XPS), transmission electron microscope (TEM), Raman, and Fourier-transform infrared spectroscopy (FTIR). The XRD results suggest that the prepared samples have an anatase crystalline structure. All of the composites tested exhibited improved photocatalytic activities as measured by the degradation of methylene blue and phenol under visible light irradiation. This improvement was attributed to the synergistic effect of Ti(3+) self-doping on TiO2 nanorods and boron doping on graphene.

  8. Fabrication of Ni-doped BiVO4 semiconductors with enhanced visible-light photocatalytic performances for wastewater treatment

    NASA Astrophysics Data System (ADS)

    Regmi, Chhabilal; Kshetri, Yuwaraj K.; Kim, Tae-Ho; Pandey, Ramesh Prasad; Ray, Schindra Kumar; Lee, Soo Wohn

    2017-08-01

    A visible-light-driven Ni-doped BiVO4 photocatalyst was synthesized using a microwave hydrothermal method. The nominal Ni doping amount of 1 wt% provided excellent photoactivity for a variety of water pollutants, such as ibuprofen (pharmaceutical), Escherichia coli (bacteria), and green tides (phytoplankton). Each Ni-doped BiVO4 sample exhibits better performance than pure BiVO4. The degradation of ibuprofen reaches 80% within 90 min, the deactivation of Escherichia coli reaches around 92% within 5 h, and the inactivation of green tide (Chlamydomonas pulsatilla) reaches 70% upon 60 min of the visible light irradiation. The first principle calculation and thermodynamic modeling revealed that Ni doping in the vanadium site gives the most stable configuration of the synthesized samples with the formation of an in-gap energy state and oxygen vacancies. The in-gap energy state and the oxygen vacancies serve as an electron-trapping center that decreases the migration time of the photogenerated carrier and increases the separation efficiency of electron-hole pairs, which are responsible for the observed efficient photocatalytic, anti-bacterial and anti-algal activity of the samples. These properties thus suggest potential applications of Ni-doped BiVO4 as a multifunctional material in the field of wastewater treatment.

  9. Electrochemically synthesized visible light absorbing vertically aligned N-doped TiO{sub 2} nanotube array films

    SciTech Connect

    Antony, Rajini P.; Mathews, Tom; Ajikumar, P.K.; Krishna, D. Nandagopala; Dash, S.; Tyagi, A.K.

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► Single step electrochemical synthesis of N-doped TiO{sub 2} nanotube array films. ► Effective substitutional N-doping achieved. ► Different N-concentrations were achieved by varying the N-precursor concentration in the electrolyte. ► Visible light absorption observed at high N-doping. -- Abstract: Visible light absorbing vertically aligned N-doped anatase nanotube array thin films were synthesized by anodizing Ti foils in ethylene glycol + NH{sub 4}F + water mixture containing urea as nitrogen source. Different nitrogen concentrations were achieved by varying the urea content in the electrolyte. The structure, morphology, composition and optical band gap of the nanotube arrays were determined by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy, respectively. The substitution of O{sup 2−} ions by N{sup 3−} ions in the anion sublattice as well as the formulae of the doped samples was confirmed from the results of XPS. The optical band gap of the nanotube arrays was found to decrease with N-concentration. The sample with the highest concentration corresponding to the formula TiO{sub 1.83}N{sub 0.14} showed two regions in the Tauc's plot indicating the presence of interband states.

  10. Remarkable photo-catalytic degradation of malachite green by nickel doped bismuth selenide under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Kulsi, Chiranjit; Ghosh, Amrita; Mondal, Anup; Kargupta, Kajari; Ganguly, Saibal; Banerjee, Dipali

    2017-01-01

    Bismuth selenide (Bi2Se3) and nickel (Ni) doped Bi2Se3 were prepared by a solvothermal approach to explore the photo-catalytic performance of the materials in degradation of malachite green (MG). The presence of nickel was confirmed by X-ray photoelectron spectroscopy (XPS) measurement in doped Bi2Se3. The results showed that the nickel doping played an important role in microstructure and photo-catalytic activity of the samples. Nickel doped Bi2Se3 sample exhibited higher photo-catalytic activity than that of the pure Bi2Se3 sample under visible-light irradiation. The photo-catalytic degradation followed first-order reaction kinetics. Fast degradation kinetics and complete (100% in 5 min of visible light irradiation) removal of MG was achieved by nickel doped Bi2Se3 in presence of hydrogen peroxide (H2O2) due to modification of band gap energies leading to suppression of photo-generated electron-hole recombination.

  11. Visible-light activity of N-LiInO2: Band structure modifications through interstitial nitrogen doping

    NASA Astrophysics Data System (ADS)

    Xu, Kaiqiang; Xu, Difa; Zhang, Xiangchao; Luo, Zhuo; Wang, Yutang; Zhang, Shiying

    2017-01-01

    Element doping is a promising strategy to improve the photo-response and photocatalytic activity of semiconductor photocatalyst with a wide band gap. To reduce the band gap of LiInO2 that is considered as a novel photocatalyst, nitrogen-doped LiInO2 (N-LiInO2) is successfully fabricated by treating LiInO2 and urea at 200 °C. It is found that interstitial instead of substitutional configurations are formed in the crystal structure of N-LiInO2 due to the low-treating temperature and rich-oxygen conditions. The interstitial N-doping forms a doping state with 0.6 eV above the valence band maximum and a defect state with 0.1 eV below the conduction band minimum, reducing the band gap of LiInO2 from 3.5 to 2.8 eV. N-LiInO2 exhibits higher photocatalytic activity towards methylene blue (MB) degradation under 380 nm light irradiation, which is 1.4 times that of pure LiInO2. The enhanced photocatalytic activity of N-LiInO2 is attributed to the extended light absorption and the improved charge carrier separation, which result in more reactive species participating in the photcatalytic process. This work provides a further understanding on tuning the band structure of semiconductor photocatalyst by N-doping strategies.

  12. Strong Energy-momentum Dispersion of Phonon Dressed Carriers in the Lightly Doped Band Insulator SrTiO3

    SciTech Connect

    Meevasana, Warawat

    2010-05-26

    Much progress has been made recently in the study of the effects of electron-phonon (el-ph) coupling in doped insulators using angle resolved photoemission (ARPES), yielding evidence for the dominant role of el-ph interactions in underdoped cuprates. As these studies have been limited to doped Mott insulators, the important question arises how this compares with doped band insulators where similar el-ph couplings should be at work. The archetypical case is the perovskite SrTiO{sub 3} (STO), well known for its giant dielectric constant of 10000 at low temperature, exceeding that of La{sub 2}CuO{sub 4} by a factor of 500. Based on this fact, it has been suggested that doped STO should be the archetypical bipolaron superconductor. Here we report an ARPES study from high-quality surfaces of lightly doped SrTiO{sub 3}. Comparing to lightly doped Mott insulators, we find the signatures of only moderate electron-phonon coupling: a dispersion anomaly associated with the low frequency optical phonon with a {lambda}{prime} {approx} 0.3 and an overall bandwidth renormalization suggesting an overall {lambda}{prime} {approx} 0.7 coming from the higher frequency phonons. Further, we find no clear signatures of the large pseudogap or small polaron phenomena. These findings demonstrate that a large dielectric constant itself is not a good indicator of el-ph coupling and highlight the unusually strong effects of the el-ph coupling in doped Mott insulators.

  13. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

    PubMed Central

    2013-01-01

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail. PMID:24369051

  14. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

    2013-12-01

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

  15. Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors.

    PubMed

    Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

    2013-12-26

    Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

  16. Erbium-doped amorphous silicon nitride light emitters for on-chip photonics applications

    NASA Astrophysics Data System (ADS)

    Yerci, Selcuk

    Silicon Photonics is considered as a viable, scalable and cost-effective solution to "the interconnect bottleneck" problem. However, the engineering of complementary metal oxide semiconductor (CMOS) compatible light sources is considered the biggest challenge of silicon photonics. Er-doped silicon-based structures are very promising candidates for 1.54 pm operation. Although Er-doped fiber lasers and amplifiers are available for long-haul communications, the small emission cross section of Er severely limits the applicability to small footprint (˜2.5 cm2) optical chip applications due to the small gain x length product. As a result, engineering strategies to boost emission efficiency and optical gain under both optical and electrical pumping in Er-doped CMOS materials need to be developed. Recently, energy sensitization of Er ions through Si-nanocrystals in Si-rich SiO2 films (Er:SRO) has been demonstrated with excitation cross sections (sigmaexc) of Er ions four-five orders of magnitude larger than sigmaabs. However, this approach suffers from the substantial free carrier losses introduced by Si-nanocrystals and the low fraction of optically active Er ions preventing net optical gain. Hence, novel materials approaches need to be developed. In this thesis, Er-doped amorphous silicon nitride (Er:SiNx) by N2 reactive sputtering is developed as a CMOS compatible platform for light sources operating under both optical and electrical pumping. The origin of visible PL of SiNx is explained by radiative transitions via localized states at the band-tails of SiNx. The efficient energy transfer between the localized band tails states in SiNx and Er ions is discussed and, sigmaexc is quantified. By performing temperature dependent studies, we demonstrated that the energy transfer is phonon-mediated. Er PL intensity and lifetime are optimized in ErSiN x by varying the fabrication parameters and a fundamental trade-off between Er excitation and emission efficiencies is

  17. Device characteristics of organic light-emitting diodes based on electronic structure of the Ba-doped Alq3 layer.

    PubMed

    Lim, Jong Tae; Kim, Kyung Nam; Yeom, Geun Young

    2009-12-01

    Organic light-emitting diodes (OLEDs) with a Ba-doped tris(8-quinolinolato)aluminum(III) (Alq3) layer were fabricated to reduce the barrier height for electron injection and to improve the electron conductivity. In the OLED consisting of glass/ITO/4,4',4"-tris[2-naphthylphenyl-1-phenylamino]triphenylamine (2-TNATA, 30 nm)/4,4'-bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (NPB, 18 nm)/Alq3 (42 nm)/Ba-doped Alq3 (20 nm, x%: x = 0, 10, 25, and 50)/Al (100 nm), the device with the Alq3 layer doped with 10% Ba showed the highest light out-coupling characteristic. However, as the Ba dopant concentration was increased from 25% to 50%, this device characteristic was largely reduced. The characteristics of these devices were interpreted on the basis of the chemical reaction between Ba and Alq3 and the electron injection property by analyzing the electronic structure of the Ba-doped Alq3 layer. At a low Ba doping of 10%, mainly the Alq3 radical anion species was formed. In addition, the barrier height for electron injection in this layer was decreased to 0.6 eV, when compared to the pristine Alq3 layer. At a high Ba doping of 50%, the Alq3 molecules were severely decomposed. When the Ba dopant concentration was changed, the light-emitting characteristics of the devices were well coincided with the formation mechanism of Alq3 radical anion and Alq3 decomposition species.

  18. Efficiency enhancement in AlGaN deep ultraviolet light-emitting diodes by adjusting Mg doped staggered barriers

    NASA Astrophysics Data System (ADS)

    Sun, Jie; Sun, Huiqing; Yi, Xinyan; Yang, Xian; Liu, Tianyi; Wang, Xin; Zhang, Xiu; Fan, Xuancong; Zhang, Zhuding; Guo, Zhiyou

    2017-07-01

    Ultraviolet light-emitting diodes (UVLEDs) with staggered barriers have been studied. The energy band diagrams, internal quantum efficiency, total output power and radiative recombination rate are investigated by APSYS software. The simulation results show that the UVLED with staggered barriers get a little enhancement comparing to the conventional one, on the contrary the structure with p-doped staggered barriers has higher efficiency and power due to enhancement of the holes' injection and the electrons' confinement. Then structures with different Al content in the Mg-doped barriers have been studied numerically and that confirmed the best.

  19. Significant enhancement of the intergrain coupling in lightly F-doped SmFeAsO superconductors

    NASA Astrophysics Data System (ADS)

    Singh, Shiv Jee; Shimoyama, Jun-ichi; Yamamoto, Akiyasu; Ogino, Hiraku; Kishio, Kohji

    2013-06-01

    A series of polycrystalline SmFeAsO1-xFx bulks (x = 0-0.25) were synthesized by a one step solid state reaction method at a low heat temperature of 900 ° C, which was about 300 ° C lower than the conventional temperature (˜1200 ° C). The magnetic susceptibility measurements showed single step superconducting transitions for the lightly doped samples with 0.05 ≤ x ≤ 0.12, while the double-step-like transitions were observed in samples x ≥ 0.15, indicating weak-link behavior of the grains. The double step transition is due to the possible occurrence of intergranular (at low temperature) and intragranular (near Tc) superconductivity consisting of coupled superconducting grains, and becomes broad with increasing x. The lightly doped samples with x = 0.10-0.12 have the onset Tc up to 51 K and the intergranular critical current density of over 103 A cm-2 at 5 K in self-field. This intergrain Jc value is one order of magnitude higher than the optimally doped samples (x = 0.2, Tc = 57 K), as assessed by remanent magnetization measurements. These results suggest strong intergrain coupling, and are expected to motivate future research and development for lightly fluorine-doped regions of REFeAs(O, F) superconductors.

  20. Carbon coating stabilized Ti(3+)-doped TiO2 for photocatalytic hydrogen generation under visible light irradiation.

    PubMed

    Fu, Gao; Zhou, Peng; Zhao, Meiming; Zhu, Weidong; Yan, Shicheng; Yu, Tao; Zou, Zhigang

    2015-07-28

    Self-doping by Ti(3+) is a useful method to expand the light response of TiO2 into the visible light region. However, to obtain a stable Ti(3+)-doped TiO2 seems to be a challenge due to the easy oxidation of Ti(3+) during the heterogeneous reaction. Here, we propose a simple carbon coating route to stabilize the Ti(3+)-doped TiO2, in which both the Ti(3+) and precursor of the carbon coating layer were in situ formed from the hydrothermal hydrolysis of titanium isopropoxide. The carbon coated Ti(3+)-doped TiO2 exhibited excellent stability for photocatalytic hydrogen production. Based on electron paramagnetic resonance (EPR) analysis, the proposed stabilizing mechanism is that the conductive carbon coating layer as a barrier layer prevents the H2O and O2 from diffusing into the surface of the photocatalyst, which can oxidize the surface O vacancies and Ti(3+) in TiO2. Our findings offer a simple route to prepare a highly stable TiO2-based photocatalyst with visible light response.

  1. Analysis and calculation of electronic properties and light absorption of defective sulfur-doped silicon and theoretical photoelectric conversion efficiency.

    PubMed

    Jiang, He; Chen, Changshui

    2015-04-23

    Most material properties can be traced to electronic structures. Black silicon produced from SF6 or sulfur powder via irradiation with femtosecond laser pulses displays decreased infrared absorption after annealing, with almost no corresponding change in visible light absorption. The high-intensity laser pulses destroy the original crystal structure, and the doping element changes the material performance. In this work, the structural and electronic properties of several sulfur-doped silicon systems are investigated using first principle calculations. Depending on the sulfur concentration (level of doping) and the behavior of the sulfur atoms in the silicon lattice, different states or an absence of states are exhibited, compared with the undoped system. Moreover, the visible-infrared light absorption intensities are structure specific. The results of our theoretical calculations show that the conversion efficiency of sulfur-doped silicon solar cells depends on the sulfur concentrations. Additionally, two types of defect configurations exhibit light absorption characteristics that differ from the other configurations. These two structures produce a rapid increase in the theoretical photoelectric conversion efficiency in the range of the specific chemical potential studied. By controlling the positions of the atomic sulfur and the sulfur concentration in the preparation process, an efficient photovoltaic (PV) material may be obtainable.

  2. Enhanced visible light photocatalytic properties of Fe-doped TiO2 nanorod clusters and monodispersed nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Wei, J. H.; Xiong, R.; Pan, C. X.; Shi, J.

    2011-07-01

    In order to get photocatalysts with desired morphologies and enhanced visible light responses, the Fe-doped TiO2 nanorod clusters and monodispersed nanoparticles were prepared by modified hydrothermal and solvothermal method, respectively. The microstructures and morphologies of TiO2 crystals can be controlled by restraining the hydrolytic reaction rates. The Fe-doped photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy (UV-vis), N2 adsorption-desorption measurement (BET), and photoluminescence spectroscopy (PL). The refinements of the microstructures and morphologies result in the enhancement of the specific surface areas. The Fe3+-dopants in TiO2 lattices not only lead to the significantly extending of the optical responses from UV to visible region but also diminish the recombination rates of the electrons and holes. The photocatalytic activities were evaluated by photocatalytic decomposition of formaldehyde in air under visible light illumination. Compared with P25 (TiO2) and N-doped TiO2 nanoparticles, the Fe-doped photocatalysts show high photocatalytic activities under visible light.

  3. Carbon-Doped Mesoporous Anatase TiO2 Multi-Tubes Nanostructures for Highly Improved Visible Light Photocatalytic Activity.

    PubMed

    Purbia, Rahul; Borah, Rituraj; Paria, Santanu

    2017-08-21

    Development of a high surface area and efficient visible light induced photocatalyst on a large scale is a promising task from the practical perspective. In this study, visible light active C-doped anatase TiO2 multi-tubes were synthesized using banana (Musa acuminata) stem fiber as a sacrificial template, removed by calcination at 450 °C. During the calcination process, the lattice of anatase TiO2 phase was doped with C, and obtained multi-tubes showed high surface area (∼99 m(2)/g) with a mesoporous structure made of ∼15 ± 3 nm nanoparticles. The synthesized TiO2 multi-tubes showed an enhanced light absorption property in the whole visible light region and good thermal stability of the anatase phase up to 750 °C. The synthesized C-doped TiO2 multi-tubes manifest an excellent photocatalytic activity for the reduction of Cr (VI) to Cr(III) under the visible light exposure. This process may have lots of practical importance as the method of synthesis of the catalyst is novel and the multi-tubes structure can be synthesized on a large scale through a quick and economical way with excellent photocatalytic activity. This novel multi-tubes structure may also be useful for photovoltaics, antimicrobial, and Li-batteries applications in the future.

  4. N-polar III-nitride quantum well light-emitting diodes with polarization-induced doping

    SciTech Connect

    Verma, Jai; Simon, John; Protasenko, Vladimir; Kosel, Thomas; Xing, Huili Grace; Jena, Debdeep

    2011-10-24

    Nitrogen-polar III-nitride heterostructures present unexplored advantages over Ga(metal)-polar crystals for optoelectronic devices. This work reports N-polar III-nitride quantum-well ultraviolet light-emitting diodes grown by plasma-assisted molecular beam epitaxy that integrate polarization-induced p-type doping by compositional grading from GaN to AlGaN along N-face. The graded AlGaN layer simultaneously acts as an electron blocking layer while facilitating smooth injection of holes into the active region, while the built-in electric field in the barriers improves carrier injection into quantum wells. The enhanced doping, carrier injection, and light extraction indicate that N-polar structures have the potential to exceed the performance of metal-polar ultraviolet light-emitting diodes.

  5. White light emission of dysprosium doped lanthanum calcium phosphate oxide and oxyfluoride glasses

    NASA Astrophysics Data System (ADS)

    Luewarasirikul, N.; Kim, H. J.; Meejitpaisan, P.; Kaewkhao, J.

    2017-04-01

    Lanthanum calcium phosphate oxide and oxyfluoride glasses doped with dysprosium oxide were prepared by melt-quenching technique with chemical composition 20La2O3:10CaO:69P2O5:1Dy2O3 and 20La2O3:10CaF2:69P2O5:1Dy2O3. The physical, optical and luminescence properties of the glass samples were studied to evaluate their potential to using as luminescence materials for solid-state lighting applications. The density, molar volume and refractive index of the glass samples were carried out. The optical and luminescence properties were studied by investigating absorption, excitation, and emission spectra of the glass samples. The absorption spectra were investigated in the UV-Vis-NIR region from 300 to 2000 nm. The excitation spectra observed under 574 nm emission wavelength showed the highest peak centered at 349 nm (6H15/2 → 6P7/2). The emission spectra, excited with 349 nm excitation wavelength showed two major peaks corresponding to 482 nm blue emission (4F9/2 → 6H15/2) and 574 nm yellow emission (4F9/2 → 6H13/2). The experimental lifetime were found to be 0.539 and 0.540 for oxide and oxyfluoride glass sample, respectively. The x,y color coordinates under 349 nm excitation wavelength were (0.38, 0.43) for both glass samples, that be plotted in white region of CIE 1931 chromaticity diagram. The CCT values obtained from the glass samples are 4204 K for oxide glass and 4228 K for oxyfluoride glass corresponding to the commercial cool white light (3100-4500 K). Judd-Ofelt theory had also been employed to obtain the J-O parameters (Ω2, Ω4 and Ω6), oscillator strength, radiative transition possibility, stimulated emission cross section and branching ratio. The Ω2 > Ω4 > Ω6 trend of J-O parameters of both glass samples may indicate the good quality of a glass host for using as optical device application. Temperature dependence of emission spectra was studied from 300 K to 10 K and found that the intensity of the emission peak was found to be increased with

  6. Optical Dependence of Electrically Detected Magnetic Resonance in Lightly Doped Si:P Devices

    NASA Astrophysics Data System (ADS)

    Zhu, Lihuang; van Schooten, Kipp J.; Guy, Mallory L.; Ramanathan, Chandrasekhar

    2017-06-01

    Using frequency-modulated electrically detected magnetic resonance (EDMR), we show that signals measured from lightly doped (1.2 - 5 ×1 015 cm-3 ) silicon devices vary significantly with the wavelength of the optical excitation used to generate the mobile carriers. We measure EDMR spectra at 4.2 K as a function of modulation frequency and applied microwave power using a 980-nm laser, a 405-nm laser, and a broadband white-light source. EDMR signals are observed from the phosphorus donor and two distinct defect species in all of the experiments. With near-infrared irradiation, we find that the EDMR signal primarily arises from donor-defect pairs, while, at higher photon energies, there are significant additional contributions from defect-defect pairs. The contribution of spins from different spatial regions to the EDMR signal is seen to vary as the optical penetration depth changes from about 120 nm at 405-nm illumination to 100 μ m at 980-nm illumination. The modulation frequency dependence of the EDMR signal shows that the energy of the optical excitation strongly modulates the kinetics of the underlying spin-dependent recombination (SDR) process. Careful tuning of the optical photon energy could therefore be used to control both the subset of spin pairs contributing to the EDMR signal and the dynamics of the SDR process.

  7. Nanophotonic coherent light-matter interfaces based on rare-earth-doped crystals

    NASA Astrophysics Data System (ADS)

    Zhong, Tian; Kindem, Jonathan M.; Miyazono, Evan; Faraon, Andrei

    2015-09-01

    Quantum light-matter interfaces connecting stationary qubits to photons will enable optical networks for quantum communications, precise global time keeping, photon switching and studies of fundamental physics. Rare-earth-ion-doped crystals are state-of-the-art materials for optical quantum memories and quantum transducers between optical photons, microwave photons and spin waves. Here we demonstrate coupling of an ensemble of neodymium rare-earth-ions to photonic nanocavities fabricated in the yttrium orthosilicate host crystal. Cavity quantum electrodynamics effects including Purcell enhancement (F=42) and dipole-induced transparency are observed on the highly coherent 4I9/2-4F3/2 optical transition. Fluctuations in the cavity transmission due to statistical fine structure of the atomic density are measured, indicating operation at the quantum level. Coherent optical control of cavity-coupled rare-earth ions is performed via photon echoes. Long optical coherence times (T2~100 μs) and small inhomogeneous broadening are measured for the cavity-coupled rare-earth ions, thus demonstrating their potential for on-chip scalable quantum light-matter interfaces.

  8. Inverted Quantum-Dot Light Emitting Diode Using Solution Processed p-Type WOx Doped PEDOT:PSS and Li Doped ZnO Charge Generation Layer.

    PubMed

    Kim, Hyo-Min; Kim, Jeonggi; Lee, Jieun; Jang, Jin

    2015-11-11

    Quantum dots (QDs) are a promising material for emissive display with low-cost manufacturing and excellent color purity. In this study, we report colloidal quantum-dot light emitting diodes (QLEDs) with an inverted architecture with a solution processed charge generation layer (CGL) of p-type polymer (tungsten oxide doped poly(ethylenedioxythiophene)/polystyrenesulfonate, PSS:WOx) and n-type metal oxide (lithium doped zinc oxide, LZO). The effective charge generation in solution processed p-n junction was confirmed by capacitance-voltage (C-V) and current density-electric field characteristics. It is also demonstrated that the performances of CGL based QLEDs are very similar when various substrates with different work functions are used.

  9. A versatile thermally activated delayed fluorescence emitter for both highly efficient doped and non-doped organic light emitting devices.

    PubMed

    Tsai, Wei-Lung; Huang, Ming-Hao; Lee, Wei-Kai; Hsu, Yi-Jiun; Pan, Kuan-Chung; Huang, Yi-Hsiang; Ting, Hao-Chun; Sarma, Monima; Ho, Yu-Yi; Hu, Hung-Chieh; Chen, Chung-Chia; Lee, Meng-Ting; Wong, Ken-Tsung; Wu, Chung-Chih

    2015-09-14

    A thermally activated delayed fluorescent (TADF) emitter (DMAC-TRZ) was reported either as the emitting dopant in a host or as the non-doped (neat) emitting layer to achieve high EL EQEs of up to 26.5% and 20% in OLEDs, respectively.

  10. Wavelength-sensitive photocatalytic degradation of methyl orange in aqueous suspension over iron(III)-doped TiO2 nanopowders under UV and visible light irradiation.

    PubMed

    Wang, X H; Li, J-G; Kamiyama, H; Moriyoshi, Y; Ishigaki, T

    2006-04-06

    Well-crystallized iron(III)-doped TiO2 nanopowders with controlled Fe3+ doping concentration and uniform dopant distribution, have been synthesized with plasma oxidative pyrolysis. The photocatalytic reactivity of the synthesized TiO2 nanopowders with a mean particle size of 50-70 nm was quantified in terms of the degradation rates of methyl orange (MO) in aqueous TiO2 suspension under UV (mainly 365 and 316 nm) and visible light irradiation (mainly 405 and 436 nm). The photodecomposition of MO over TiO2 nanopowders followed a distinct two-stage pseudo first order kinetics. Interestingly, the photocatalytic reactivity depends not only on the iron doping concentration but also on the wavelength of the irradiating light. Under UV irradiation, nominally undoped TiO2 had much higher reactivity than Fe3+ -doped TiO2, suggesting that Fe3+ doping (> 0.05 at. %) in TiO2 with a mean particle size of approximately 60 nm was detrimental to the photocatalytic decomposition of methyl orange. Whereas, under visible light irradiation, the Fe3+ -doped TiO2 with an intermediate iron doping concentration of approximately 1 at. % had the highest photocatalytic reactivity due to the narrowing of band gap so that it could effectively absorb the light with longer wavelength. A strategy for improving the photocatalytic reactivity of Fe3+ -doped TiO2 used in the visible light region is also proposed.

  11. Photocatalytic degradation of phenol by visible light-responsive iron-doped TiO2 and spontaneous sedimentation of the TiO2 particles.

    PubMed

    Nahar, Mst Shamsun; Hasegawa, Kiyoshi; Kagaya, Shigehiro

    2006-12-01

    Fe-doped TiO2 was prepared by the calcination of Fe(x)TiS(2) (x=0, 0.002, 0.005, 0.008, 0.01) and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectra. All the Fe-doped TiO2 were composed of an anatase crystal form and showed red shifts to a longer wavelength. The activity of the Fe-doped TiO2 for the degradation of phenol was investigated by varying the iron content during UV (365nm) and visible light (405nm and 436nm) irradiation. The degradation rate depended on the Fe content and the Fe-doped TiO2 was responsive to the visible light as well as the elevated activity toward UV light. The molar ratio of 0.005 was the optimum for both the UV and visible light irradiations. The result was discussed on the basis of the balance of the excited electron-hole trap by the doped Fe(3+) and their charge recombination on the doped Fe(3+) level. The Fe-doped TiO2 (x=0.005) was more active than P25 TiO2 under solar light irradiation. The suspended Fe-doped TiO2 spontaneously precipitated once the stirring of the reaction mixture was terminated.

  12. White light simulation and luminescence studies on Dy3+ doped Zinc borophosphate glasses

    NASA Astrophysics Data System (ADS)

    Vijayakumar, R.; Venkataiah, G.; Marimuthu, K.

    2015-01-01

    The Dy3+ doped Zinc borophosphate glasses with the chemical composition (79-x)B2O3+xP2O5+10Li2O+10ZnO+1Dy2O3 (where x=0, 10, 20, 30 and 50 in wt%) have been prepared by melt quenching technique. The prepared glass samples were characterized through optical absorption, emission and decay measurements. The bonding parameters, optical band gap and Urbach's energy values were calculated from the optical absorption spectra to explore the bonding nature of the Dy-O metal ligand and electronic band structure of the studied glasses. Judd-Ofelt (JO) intensity parameters were calculated from the absorption spectra by using the JO theory and it gives information about symmetry of the ligand environment around the Dy3+ ion site. The Y/B intensity ratio and radiative properties were obtained from the emission spectra and the results were compared with the reported literature. The x, y chromaticity color coordinates of the studied glasses were analyzed using a CIE 1931 color chromaticity diagram and found that the x, y coordinates lie in the white light region. The decay curve measurements of the prepared glasses exhibit non-exponential behavior and are well fitted to Inokuti-Hirayama (IH) model to understand the energy transfer mechanism between Dy3+ ions. The Q, R0 and CDA values of the prepared Dy3+ doped glasses were obtained from the IH model and the results were discussed and compared with the reported literature.

  13. Blue light emission from trivalent cerium doped in sol-gel silica glass

    NASA Astrophysics Data System (ADS)

    Tokumitsu, Seika; Murakami, Yukon; Oda, Hisaya; Kawabe, Yutaka

    2017-02-01

    Rare earths in glass matrices are promising for active optical devices as amplifiers and lasers. Emission originating from d-f transitions in sol-gel glass has not been studied very often, while those based on f-f transitions were widely utilized. However, d-f emission in rare earths is very important because of their strong oscillator strength and broad emission widths suitable for the application to scintillators and solid-state lasers. Co-doping of aluminum in sol-gel synthesis was known to be effective for the emission enhancement of trivalent terbium and europium. Recently, we applied aluminum co-doping to cerium and europium systems in sol-gel glass to succeed in the observation of strong blue light emission originating from d-f transitions. Glass samples were prepared with conventional sol-gel process where tetramethylorthosilicate was hydrolyzed in the mixture of water, ethanol and dimethylformamide with nitric acid catalyst. After adding cerium nitrate and aluminum nitrate, the solution experienced drying followed by calcination at 1,050°C under air environment. When molar ratio of cerium to silicon was adjusted at 0.1% and Al concentration was varied in 0.1 2.0%, transparent glass products showed bright and broad blue photoluminescence under UV illumination. The fluorescence lifetimes were found to be about 50 90 ns, indicating that the emission was due to d-f transitions. Considering the simplicity of the process, blue phosphors based on sol-gel glass will be very promising for future applications.

  14. Fundamental emission characteristics of light-emitting liquid crystal cells with rubrene-doped 4-cyano-4'-pentylbiphenyl

    NASA Astrophysics Data System (ADS)

    Honma, Michinori; Horiuchi, Takao; Tanimoto, Masashi; Nose, Toshiaki

    2014-06-01

    We have investigated the light emission properties in rubrene-doped nematic liquid crystal (LC) cells from the following three standpoints: (i) effect of the heating temperature during the sample preparation, (ii) role of the emissive LC layer thickness, and (iii) role of different LC types used as the emissive layer. As a result, the light-emitting LC cells simultaneously exhibit the features of electrochemiluminescent cells (the carrier transport is governed by an ionic conduction) as well as of organic light-emitting diodes (the luminance strongly depends on the emissive layer thickness). Furthermore, we report that devices with cyano group containing LCs exhibit higher luminance compared to a fluorinated LC.

  15. Preparation and Solar Light Photocatalytic Activity of N-Doped TiO2-Loaded Halloysite Nanotubes Nanocomposites

    NASA Astrophysics Data System (ADS)

    Cheng, Zhi-Lin; Sun, Wei

    2015-10-01

    A novel method to prepare N-doped TiO2-loaded halloysite nanotubes (N-TiO2/HNTs) nanocomposites was achieved by using the chemical vapor deposition in autoclave. The N-TiO2/HNTs nanocomposites obtained by the different form of the doping N source were studied through a series of characterizations. The XRD, SEM, and TEM characterizations verified the anatase structure of TiO2 nanoparticles with the size of ca.20nm loaded on the outer surface of HNTs. The UV-vis characterization of the N-TiO2/HNTs presented a further red-shift compared to the pure N-TiO2 nanoparticles.. The XPS characterizations confirmed the N element doped into the crystal structure of TiO2 nanoparticles. The photocatalytic activities of N-TiO2/HNTs nanocomposites prepared were evaluated by degradation of phenol at room temperature under simulated solar light irradiation.

  16. Pavement base drain evaluation

    NASA Astrophysics Data System (ADS)

    Hoffman, G. L.

    1981-06-01

    Portions of a highway drainage system design was revised. Essentially, the longitudinal drainage trench was moved closer to the pavement/shoulder joint, and the fine concrete sand layer was eliminated as a trench backfill material. The specified backfill material is a coarser crushed aggregate (pea gravel). An evaluation of the effects of these changes on pavement performance is given and the new pavement base drain system is compared to the older pipe foundation underdrain system at the same site.

  17. Integrating planar waveguides doped with light scattering nanoparticles into a flat-plate photobioreactor to improve light distribution and microalgae growth.

    PubMed

    Sun, Yahui; Liao, Qiang; Huang, Yun; Xia, Ao; Fu, Qian; Zhu, Xun; Zheng, Yaping

    2016-11-01

    Industrially manufactured planar waveguides doped with light scattering nanoparticles, which can dilute and redistribute the intense incident light within microalgae suspension more uniformly, were introduced into a flat-plate photobioreactor (PBR) with a width of 25cm to alleviate the adverse effect of poor light penetrability on microalgae growth. Compared with the flat-plate PBR without waveguides, the illumination surface area per unit volume in the proposed PBR was increased by 10.3 times. During the whole cultivation period, the illuminated volume fractions in the proposed PBR were 21.4-410% higher than those in the flat-plate PBR without waveguides. Consequently, attributed to the optimized light distribution in the proposed PBR, a 220% improvement in biomass production was obtained relative to that in the flat-plate PBR without waveguides. Furthermore, higher light output intensities emitted from the planar waveguide surfaces and increased microalgae growth rates were achieved by decreasing the length of planar waveguides.

  18. Influence of p-doping hole transport layer on the performance of organic light-emitting devices

    NASA Astrophysics Data System (ADS)

    Khan, M. A.; Xu, Wei; Khizar-ul-Haq; Bai, Yu; Jiang, X. Y.; Zhang, Z. L.; Zhu, W. Q.

    2008-05-01

    We have demonstrated devices based on a p-doped layer consisting of 4,4',4''-tris(3-methylphenylphenylamono) triphenylamine (m-MTDATA) and tetrafluro-tetracyano-quinodimethane (F4-TCNQ) as a hole transport layer (HTL). The typical device structure is ITO/m-MTDATA: x% F4-TCNQ (40 nm)/N, N'-bis-[1-naphthy(-N, N' diphenyl-1,1'-biphenyl-4,4'-diamine)] (NPB) (10 nm)/tris (8-hydroxyquinoline) aluminum (Alq3) (50 nm)/LiF (10 nm)/Al (100 nm). Hole-only devices, where the current only consists of holes, are fabricated to observe the apparent improvement in the conductivity of the p-doped layers. We have observed that such layers lead to a striking improvement of the electrical properties of organic light-emitting devices. In particular, the electroluminescent onset voltage is observed to decrease continuously with increasing doping ratio and is greatly reduced compared to diodes with undoped layers. We have seen that the driving voltage of device 3 (m-MTDATA:4% F4-TCNQ) is reduced ~56% as compared with that of the control device (undoped). This improvement has been attributed to the increased conductivity of the p-doping hole transport layer. It is found that the current efficiency also decreases with increasing doping ratio. This can be attributed to the charge imbalance in the emission layer due to the excess hole injection.

  19. Ultrasonic synthesis and photocatalytic performance of metal-ions doped TiO{sub 2} catalysts under solar light irradiation

    SciTech Connect

    Feng, Huajun; Yu, Liya E.; Zhang, Min-Hong

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► We synthesized eight metal-ions doped TiO{sub 2} catalysts by a unique ultrasonic method. ► Mg-doped TiO{sub 2} showed the highest photocatalytic performance under solar light. ► Surface area of catalyst dominates the photocatalytic efficiency under solar light. ► Crystal property and visible light activity are less important than surface area. -- Abstract: Eight metal-ions doped TiO{sub 2} (M-TiO{sub 2}) were successfully synthesized by an ultrasonic method, including Fe, Co, Ce, Cr, Mn, Mg, Ni and Ag ions. Among them, the 1% Mg–TiO{sub 2} shows the highest photocatalytic efficiency under solar light, which was determined by degrading rhodamine B (RhB) molecules in an aqueous solution. The synthesized M-TiO{sub 2} samples were characterized by XRD, BET Surface area, TEM, XPS and diffuse reflectance spectrum. Effects of synthesis conditions and characterized properties on photocatalytic efficiency of the M-TiO{sub 2} were investigated comprehensively. A positive correlation between specific surface area and photocatalytic efficiency of the M-TiO{sub 2} was found across different synthesis conditions. However, no clear correlation with photocatalytic efficiency was observed for crystal structure and radii of doping ions of the M-TiO{sub 2}. XPS study indicates the change of oxidation states of Mn ions in Mn–TiO{sub 2} during synthesis procedure from the initial Mn{sup 2+} to a mixture of Mn{sup 3+} and Mn{sup 4+} ions. Dye sensitization mechanism was observed during the photocatalytic procedure of the Mg–TiO{sub 2}, which enhanced the degradation efficiency of the Mg–TiO{sub 2} under solar light. Finally, no obvious loss of photocatalytic activity was observed for the Mg–TiO{sub 2} after five cycles of RhB degradation.

  20. Wavelength dependence and multiple-induced states in photoresponses of copper phthalocyanine-doped gold nanoparticle single-electron device

    NASA Astrophysics Data System (ADS)

    Yamamoto, Makoto; Ueda, Rieko; Terui, Toshifumi; Imazu, Keisuke; Tamada, Kaoru; Sakano, Takeshi; Matsuda, Kenji; Ishii, Hisao; Noguchi, Yutaka

    2014-01-01

    We have proposed a gold nanoparticle (GNP)-based single-electron transistor (SET) doped with a dye molecule, where the molecule works as a photoresponsive floating gate. Here, we examined the source-drain current (I_{\\text{SD}}) at a constant drain voltage under light irradiation with various wavelengths ranging from 400 to 700 nm. Current change was enhanced at the wavelengths of 600 and 700 nm, corresponding to the optical absorption band of the doped molecule (copper phthalocyanine: CuPc). Moreover, several peaks appear in the histograms of I_{\\text{SD}} during light irradiation, indicating that multiple discrete states were induced in the device. The results suggest that the current change was initiated by the light absorption of CuPc and multiple CuPc molecules near the GNP working as a floating gate. Molecular doping can activate advanced device functions in GNP-based SETs.

  1. Enhanced visible light activity of nano-titanium dioxide doped with multiple ions: Effect of crystal defects

    SciTech Connect

    Jaimy, Kanakkanmavudi B.; Ghosh, Swapankumar; Gopakumar Warrier, Krishna

    2012-12-15

    Titanium dioxide photocatalysts co-doped with iron(III) and lanthanum(III) have been prepared through a modified sol-gel method. Doping with Fe{sup 3+} resulted in a relatively lower anatase to rutile phase transformation temperature, while La{sup 3+} addition reduced the crystal growth and thus retarded the phase transformation of titania nanoparticles. The presence of Fe{sup 3+} ions shifted the absorption profile of titania to the longer wavelength side of the spectrum and enhanced the visible light activity. On the other hand, La{sup 3+} addition improved the optical absorption of titania nanoparticles. Both the dopants improved the life time of excitons by proper transferring and trapping of photoexcited charges. In the present work, considerable enhancement in photocatalytic activity under visible light was achieved through synergistic effect of optimum concentrations of the two dopants and associated crystal defects. - Graphical abstract: Photocatalytic activity studies indicate a synergistic effect of dopants and crystal defects leading to an enhanced photochemical activity. Highlights: Black-Right-Pointing-Pointer An aqueous sol-gel synthesis of Fe{sup 3+} and La{sup 3+} co-doped TiO{sub 2} is being reported. Black-Right-Pointing-Pointer Optical and microstructural properties of titania were modified by co-doping. Black-Right-Pointing-Pointer Enhanced activity of titania by the crystal defects is being reported.

  2. Electronic and optical properties of N-doped Bi2O3 polymorphs for visible light-induced photocatalysis.

    PubMed

    Wang, Fang; Cao, Kun; Wu, Yi; Patzke, Greta R; Zhou, Ying

    2015-03-01

    The effect of N doping on the crystal structure, electronic, and optical properties of α-Bi2O3 and β-Bi2O3 has been studied in detail based with first principle calculations. The crystallographic features of Bi2O3 polymorphs are not substantially changed through N doping, whereas charge transfer from Bi to N results in large variations of charge density distribution. N-doped β-Bi2O3 exhibits improved thermal stability due to stronger Bi-N covalent bonds and lower defect formation energy, and the convenient preparative access agrees well with experimental observations. Calculated band structures and optical properties indicate that N doping does not induce major band gap narrowing, but leads to the presence of isolated bands above the VBM induced by N 2p for both α-Bi2O3 and β-Bi2O3 which induce large red-shifts of their visible light absoprtion properties. These isolated bands act as acceptor levels and facilitate electron transition under visible light illumination through introduction of steps between VB and CB, thereby rendering the materials quite promising for photocatalytic applications.

  3. Template-free synthesis of mesoporous N-doped SrTiO3 perovskite with high visible-light-driven photocatalytic activity.

    PubMed

    Zou, Fei; Jiang, Zheng; Qin, Xiaoqin; Zhao, Yongxiang; Jiang, Luyun; Zhi, Jinfang; Xiao, Tiancun; Edwards, Peter P

    2012-09-04

    An effective, template-free synthesis methodology has been developed for preparing mesoporous nitrogen-doped SrTiO(3) (meso-STON) using glycine as both a nitrogen source and a mesopore creator. The N-doping, large surface area and developed porosity endow meso-STON with excellent activity in visible-light-responsive photodegradation of organic dyes.

  4. Plasmon resonance and perfect light absorption in subwavelength trench arrays etched in gallium-doped zinc oxide film

    SciTech Connect

    Hendrickson, Joshua R. Leedy, Kevin; Cleary, Justin W.; Vangala, Shivashankar; Nader, Nima; Guo, Junpeng

    2015-11-09

    Near-perfect light absorption in subwavelength trench arrays etched in highly conductive gallium-doped zinc oxide films was experimentally observed in the mid infrared regime. At wavelengths corresponding to the resonant excitation of surface plasmons, up to 99% of impinging light is efficiently trapped and absorbed in the periodic trenches. Scattering cross sectional calculations reveal that each individual trench acts like a vertical split ring resonator with a broad plasmon resonance spectrum. The coupling of these individual plasmon resonators in the grating structure leads to enhanced photon absorption and significant resonant spectral linewidth narrowing. Ellipsometry measurements taken before and after device fabrication result in different permittivity values for the doped zinc oxide material, indicating that localized annealing occurred during the plasma etching process due to surface heating. Simulations, which incorporate a 50 nm annealed region at the zinc oxide surface, are in a good agreement with the experimental results.

  5. Preparation, characterization and visible light photocatalytic activity of silver, nitrogen co-doped TiO2 photocatalyst

    NASA Astrophysics Data System (ADS)

    Khan, Matiullah; Ramin Gul, Sahar; Li, Jing; Cao, Wenbin; Mamalis, Athanasios G.

    2015-06-01

    TiO2 photocatalyst codoped with Silver (Ag) and Nitrogen (N) with different Ag doping concentrations is successfully synthesized by hydrothermal method. The as-synthesized samples are characterized through x-ray diffraction (XRD), Transmission electron microscopy (TEM), UV-vis. absorption spectra and x-ray photoelectron spectroscopy (XPS). The photocatalytic response is evaluated by the photodegradation of methylene blue under visible light irradiations. All synthesized samples are composed of pure anatase phase with good crystallinity. The absorption edge of codoped TiO2 is shifted towards visible light region. X-ray photoelectron spectroscopy confirmed the existence of silver and nitrogen in the codoped samples. All the codoped samples demonstrated improved photocatalytic activity compared to pure TiO2. Among the different codoped samples, the one with silver doping concentration of 4 at. % exhibited the highest photoactivity.

  6. Electrospun nanofibers of Bi-doped TiO2 with high photocatalytic activity under visible light irradiation.

    PubMed

    Xu, Jie; Wang, Wenzhong; Shang, Meng; Gao, Erping; Zhang, Zhijie; Ren, Jia

    2011-11-30

    Bi-doped TiO(2) nanofibers with different Bi content were firstly prepared by an electrospinning method. The as-prepared nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence spectra (PL), and UV-vis diffuse reflectance spectroscopy (DRS). The results indicated that Bi(3+) ions were successfully incorporated into TiO(2) and extended the absorption of TiO(2) into visible light region. The photocatalytic experiments showed that Bi-doped TiO(2) nanofibers exhibited higher activities than sole TiO(2) in the degradation of rhodamine B (RhB) and phenol under visible light irradiation (λ>420 nm), and 3% Bi:TiO(2) samples showed the highest photocatalytic activities.

  7. Effect of synergy on the visible light activity of B, N and Fe co-doped TiO2 for the degradation of MO.

    PubMed

    Xing, Mingyang; Wu, Yongmei; Zhang, Jinlong; Chen, Feng

    2010-07-01

    Single doped, co-doped and tri-doped TiO(2) with B, N and Fe are successfully synthesized by using the hydrothermal method. The samples are characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples are evaluated for degradation of methyl-orange (MO, 20 mg L(-1)) in aqueous solutions under visible light (lambda > 420 nm). The results of XRD suggest that all the catalysts present anatase crystal. All the doping catalysts show higher photoactivities than pure TiO(2) under visible light irradiation. In the single nonmetal doped TiO(2), the localized dopant levels near the valence band (VB) are responsible for the enhancement of photoactivies. Fe(3+) impurity level formed under the conduction band (CB) induces the high photocatalytic activities of iron doped TiO(2). In the co-doped and tri-doped catalysts, the B 2p and N 2p acceptor states contribute to the band gap narrowing by mixing with O 2p states combined with the overlapping of the conduction band by the iron "d" orbital, resulting in improvement of the photo-performance under visible light irradiation. Iron co-doped with boron catalyst shows low photoactivity under visible light due to the absence of Fe(3+) impurity levels at the bottom of the conduction band. In addition, the XPS results indicate the presence of synergistic effects in co-doped and tri-doped catalysts, which contribute to the enhancement of photocatalytic activities.

  8. Effect of synergy on the visible light activity of B, N and Fe co-doped TiO2 for the degradation of MO

    NASA Astrophysics Data System (ADS)

    Xing, Mingyang; Wu, Yongmei; Zhang, Jinlong; Chen, Feng

    2010-07-01

    Single doped, co-doped and tri-doped TiO2 with B, N and Fe are successfully synthesized by using the hydrothermal method. The samples are characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples are evaluated for degradation of methyl-orange (MO, 20 mg L-1) in aqueous solutions under visible light (λ > 420 nm). The results of XRD suggest that all the catalysts present anatase crystal. All the doping catalysts show higher photoactivities than pure TiO2 under visible light irradiation. In the single nonmetal doped TiO2, the localized dopant levels near the valence band (VB) are responsible for the enhancement of photoactivies. Fe3+ impurity level formed under the conduction band (CB) induces the high photocatalytic activities of iron doped TiO2. In the co-doped and tri-doped catalysts, the B 2p and N 2p acceptor states contribute to the band gap narrowing by mixing with O 2p states combined with the overlapping of the conduction band by the iron ``d'' orbital, resulting in improvement of the photo-performance under visible light irradiation. Iron co-doped with boron catalyst shows low photoactivity under visible light due to the absence of Fe3+ impurity levels at the bottom of the conduction band. In addition, the XPS results indicate the presence of synergistic effects in co-doped and tri-doped catalysts, which contribute to the enhancement of photocatalytic activities.

  9. Direct laser interference patterning of polystyrene films doped with azo dyes, using 355 nm laser light

    NASA Astrophysics Data System (ADS)

    Broglia, M. F.; Suarez, S.; Soldera, F.; Mücklich, F.; Barbero, C. A.; Bellingeri, R.; Alustiza, F.; Acevedo, D.

    2014-05-01

    The generation of line-like periodic patterns by direct laser interference patterning (DLIP) of polystyrene films (PS) at a wavelength of 355 nm has been investigated. No structuration is achieved in plain PS due to the weak absorption of the polymer at 355 nm. On the other hand, patterning is achieved on films doped (PSd) with an azo dye (2-anisidine → 2-anisidine) which is incorporated in the polymer solution used for film preparation. Periodic micro-structures are generated. DLIP on PSd results in the swelling of the surface at low fluences, while at high laser intensities it causes the ablation of the regions at the interference maxima positions. The results contrast with the usual process of DLIP on PS (at shorter wavelengths, like 266 nm) where only ablation is detected. The results suggest that decomposition of the azo dye is the driving force of the patterning which therefore differ from the patterning obtained when plain PS is irradiated with laser light able to be absorbed by the aromatic ring in PS (e.g. 266 nm). The biocompatibility of these materials and adhesion of cells was tested, the data from in vitro assays shows that fibroblast cells are attached and proliferate extensively on the PSd films.

  10. Photoactive Nanomaterials Inspired by Nature: LTL Zeolite Doped with Laser Dyes as Artificial Light Harvesting Systems

    PubMed Central

    Gartzia-Rivero, Leire; Bañuelos, Jorge; López-Arbeloa, Iñigo

    2017-01-01

    The herein reported work describes the development of hierarchically-organized fluorescent nanomaterials inspired by plant antenna systems. These hybrid materials are based on nanostructured zeolitic materials (LTL zeolite) doped with laser dyes, which implies a synergism between organic and inorganic moieties. The non-interconnected channeled structure and pore dimensions (7.1 Å) of the inorganic host are ideal to order and align the allocated fluorophores inside, inferring also high thermal and chemical stability. These artificial antennae harvest a broad range of chromatic radiation and convert it into predominant red-edge or alternatively white-light emission, just choosing the right dye combination and concentration ratio to modulate the efficiency of the ongoing energy transfer hops. A further degree of organization can be achieved by functionalizing the channel entrances of LTL zeolite with specific tailor-made (stopcock) molecules via a covalent linkage. These molecules plug the channels to avoid the leakage of the guest molecules absorbed inside, as well as connect the inner space of the zeolite with the outside thanks to energy transfer processes, making the coupling of the material with external devices easier. PMID:28772856

  11. The extreme quantum limit in lightly-doped SrTiO3

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Anand; Skinner, Brian; Khalsa, Guru; Suslov, Alexey

    When a three dimensional electron gas is placed in a sufficiently strong magnetic field, it is said to be in the quantum limit when the cyclotron energy ℏωc >ɛF >>kT, and all of the electrons occupy the lowest Landau level. Achieving this limit in a material requires a small Fermi energy relative to the applied magnetic field, and a weak disorder potential such that magnetic freeze-out is avoided. We present an experimental study of lightly-doped single crystals of SrTiO3, which remain good bulk conductors in temperatures down to 25 mK and magnetic fields up to 45 T. Our measurements probe deep into the quantum limit, where ℏωc >>ɛF and theory has long predicted that electron-electron interactions can drive the system into a charge density wave or Wigner crystal like state. A number of interesting features arise in electrical transport in this regime, including a striking re-entrant nonlinearity in the current-voltage characteristics. We discuss these features in the context of possible correlated electron states, and present a picture based on magnetic field induced puddling of electrons in a disorder potential landscape. U.S. DOE, BES Contract No. DE-AC02-06CH11357; NIST CNST; US NSF Cooperative Agreement No. DMR-1157490; State of Florida.

  12. Structural and luminescence properties of Dy3+ doped bismuth phosphate glasses for greenish yellow light applications

    NASA Astrophysics Data System (ADS)

    Damodaraiah, S.; Reddy Prasad, V.; Babu, S.; Ratnakaram, Y. C.

    2017-05-01

    Different compositions of (5, 10, 15 and 20 mol%) of bismuth and different concentrations (0.5, 1.0, 1.5 and 2.0 mol%) of Dy3+ ion doped bismuth phosphate (BiP) glasses were synthesized by melt-quenching technique. The structural characterization was accomplished by XRD, SEM with EDS, FTIR, FT-Raman and 31P MAS NMR spectroscopy. The optical properties were studied using absorption and photoluminescence spectroscopy. Different structural groups were identified using FTIR and FT-Raman spectra. The depolymerization of metaphosphate chains are described by the decrease of Q2 tetrahedral sites allowing the formation of pyrophosphate groups (Q1) revealed by 31P MAS NMR spectroscopic investigations. Judd-Ofelt intensity parameters Ωλ (λ = 2, 4 and 6) were evaluated from absorption spectra. Radiative parameters such as radiative lifetimes (τR), integrated absorption cross-sections (Σ) and branching ratios (βR) were calculated using Judd-Ofelt intensity parameters. From photoluminescence spectra, experimental branching ratios (βexp) and stimulated emission cross-sections (σP) were calculated for all the observed emission transitions of prepared glasses. The decay profiles for 4F9/2 level were recorded and fit exponential for 0.5 mol% and non-exponential for higher concentrations of Dy3+ due to non-radiative energy transfer among excited Dy3+ ions. The CIE chromaticity co-ordinates have been calculated from the luminescence spectra which confirmed greenish yellow light emission.

  13. Nitrogen-doped graphene oxide quantum dots as photocatalysts for overall water-splitting under visible light illumination.

    PubMed

    Yeh, Te-Fu; Teng, Chiao-Yi; Chen, Shean-Jen; Teng, Hsisheng

    2014-05-28

    Nitrogen-doped graphene oxide quantum dots exhibit both p- and n-type conductivities and catalyze overall water-splitting under visible-light irradiation. The quantum dots contain p-n type photochemical diodes, in which the carbon sp(2) clusters serve as the interfacial junction. The active sites for H2 and O2 evolution are the p- and n-domains, respectively, and the reaction mimics biological photosynthesis.

  14. Novel Na(+) doped Alq3 hybrid materials for organic light-emitting diode (OLED) devices and flat panel displays.

    PubMed

    Bhagat, S A; Borghate, S V; Kalyani, N Thejo; Dhoble, S J

    2015-05-01

    Pure and Na(+) -doped Alq3 complexes were synthesized by a simple precipitation method at room temperature, maintaining a stoichiometric ratio. These complexes were characterized by X-ray diffraction, Fourier transform infrared (FTIR), UV/Vis absorption and photoluminescence (PL) spectra. The X-ray diffractogram exhibits well-resolved peaks, revealing the crystalline nature of the synthesized complexes, FTIR confirms the molecular structure and the completion of quinoline ring formation in the metal complex. UV/Vis absorption and PL spectra of sodium-doped Alq3 complexes exhibit high emission intensity in comparison with Alq3 phosphor, proving that when doped in Alq3 , Na(+) enhances PL emission intensity. The excitation spectra of the synthesized complexes lie in the range 242-457 nm when weak shoulders are also considered. Because the sharp excitation peak falls in the blue region of visible radiation, the complexes can be employed for blue chip excitation. The emission wavelength of all the synthesized complexes lies in the bluish green/green region ranging between 485 and 531 nm. The intensity of the emission wavelength was found to be elevated when Na(+) is doped into Alq3 . Because both the excitation and emission wavelengths fall in the visible region of electromagnetic radiation, these phosphors can also be employed to improve the power conversion efficiency of photovoltaic cells by using the solar spectral conversion principle. Thus, the synthesized phosphors can be used as bluish green/green light-emitting phosphors for organic light-emitting diodes, flat panel displays, solid-state lighting technology - a step towards the desire to reduce energy consumption and generate pollution free light. Copyright © 2014 John Wiley & Sons, Ltd.

  15. A novel approach for the synthesis of visible-light-active nanocrystalline N-doped TiO2 photocatalytic hydrosol

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Xiu; Jiang, Peng; Shao, Wei-Na; Zhang, Jun; Cao, Wen-Bin

    2014-07-01

    A visible-light-active nitrogen doped nanocrystalline titanium dioxide (N-TiO2) hydrosol was prepared by precipitation-peptization method and following with hydrothermal crystallization at 110 °C holding for 6 h. XPS results show that nitrogen ions have been doped into the TiO2 lattice successfully and the UV-Vis absorption spectra indicate that the light absorption edge of the N-doped TiO2 has been red-shifted into visible light region. The photocatalytic performance of the N-doped TiO2 thin film prepared from the synthesized hydrosol was evaluated by photodegrading the gaseous formaldehyde (HCHO) under visible light irradiation. The photodegradation ratio of HCHO reached up to 90% within 24 h and the degradation ratio was stable for ten degradation cycles, indicating the prepared hydrosol has good reusable performance in photodegrading gaseous pollutants.

  16. Interlayer-I-doped BiOIO3 nanoplates with an optimized electronic structure for efficient visible light photocatalysis.

    PubMed

    Sun, Yanjuan; Xiong, Ting; Dong, Fan; Huang, Hongwei; Cen, Wanglai

    2016-07-07

    The success in the synthesis of Bi-based layered photocatalysts with high photocatalytic activities has triggered intensive studies. Herein, we prepared interlayer-I-doped BiOIO3 nanoplates by a facile method. Interestingly, it was found that I atoms were doped into the BiOIO3 interlayers instead of substituting for the lattice atoms based on theoretical and experimental results. The interbedded I atoms endowed BiOIO3 with an extended light response from the UV to the visible region by narrowing the bandgap and generating a middle level. The enhanced oxidation capability via positive-shifting the valence band position and improved carrier separation efficiency via forming charge delivery channels at the adjacent two layers can be achieved simultaneously. As expected, I-intercalated BiOIO3 with an optimized electronic structure demonstrated outstanding NO removal ability under visible light irradiation, much superior to pure BiOIO3. The present success in fabricating interlayer-I-doped BiOIO3 would open a promising route to prepare other Bi-based layered semiconductors with efficient visible-light photocatalysis.

  17. A comprehensive investigation of tetragonal Gd-doped BiVO4 with enhanced photocatalytic performance under sun-light

    NASA Astrophysics Data System (ADS)

    Luo, Yangyang; Tan, Guoqiang; Dong, Guohua; Ren, Huijun; Xia, Ao

    2016-02-01

    Tetragonal Gd-doped BiVO4 having enhanced photocatalytic activity have been synthesized by a facile microwave hydrothermal method. The structural analysis indicates that Gd doping can induce the phase transition from monoclinic to tetragonal BiVO4. The reaction results in precursor solutions imply that tetragonal GdVO4 seeds as crystal nucleus are the original and determined incentives to force the formation of tetragonal Gd-BiVO4. The influences of the surface defect, band structure, and BET surface area on the improved photocatalytic activities of tetragonal Gd-doped BiVO4 are investigated systematically. The results demonstrate that the more surface oxygen deficiencies as active sites and the excellent mobility and separation of photogenerated electrons and holes are beneficial to the enhancement of the photocatalytic performance of tetragonal Gd-BiVO4. The RhB photodegradation experiments indicate that the contribution of high photocatalytic activities under simulated sun-light is mainly from UV-light region due to the tetragonal structure feature. The best photocatalytic performance is obtained for tetragonal 10 at% Gd-BiVO4, of which the RhB degradation rate can reach to 96% after 120 min simulated sun-light irradiation. The stable tetragonal Gd-BiVO4 with efficient mineralization will be a promising photocatalytic material applied in water purification.

  18. Preparation, characterization of the Ta-doped ZnO nanoparticles and their photocatalytic activity under visible-light illumination

    SciTech Connect

    Kong Jizhou; Li Aidong; Zhai Haifa; Gong Youpin; Li Hui; Wu Di

    2009-08-15

    This paper describes a novel catalyst of the Ta-doped ZnO nanocrystals prepared by a modified polymerizable complex method using the water-soluble tantalum precursor as the sources of Ta. The catalysts were characterized by means of various analytical techniques as a function of Ta content (x=0-4 mol%) systematically. A remarkable advantage of the results was confirmed that dopant Ta enhanced the visible-light absorption of ZnO and the low-solubility tantalum doping could restrain the growth of crystal and minish the particle size. The relationship between the physicochemical property and the photocatalytic performance was discussed, and it was found that the photocatalytic activity in the photochemical degradation of methylene blue under visible-light irradiation (lambda>=420 nm) was dependent on the contents of the dopant, which could affect the particle size, concentration of surface hydroxyl groups and active hydrogen-related defect sites, and the visible-light absorption. The highest photocatalytic activity was obtained for the 1.0 mol% Ta-doped ZnO sample. - Graphical abstract: The addition of the tantalum into ZnO prepared by a modified polymerizable complex method not only restrains the growth of crystal, minish the particle size, but also changes the nanocrystal morphology.

  19. Nanostructured organic light-emitting diodes with electronic doping, transparent carbon nanotube charge injectors, and quantum dots

    NASA Astrophysics Data System (ADS)

    Williams, Christopher D.

    Organic light-emitting diodes (OLEDs) and polymeric light-emitting diodes (PLEDs) are rapidly-emerging technologies which are being studied extensively in industrial, academic, and government laboratories for applications in displays and solid-state lighting. Their thin film structure (with total thickness of active layers less than a micron) and the inherent flexibility of the constituent materials give them promise in the flat panel display industry as well as open new areas of possible applications for flexible transparent displays and even textile displays. The materials also show high electroluminescence efficiency, and with proper device engineering these devices demonstrate efficiencies and lifetimes which surpass current methods of lighting such at incandescent bulbs, which average approximately 1% efficiency. Lastly, the materials offer easy processing through well studied and developed methods such as thermal evaporation, solution spin-casting and ink jet printing. Ink jet printing of polymeric layers in PLEDs offers many advantages when considering mass production of display and lighting panels, as it allows uniform films to be produced on large area substrates using a simple roll-to-roll method. In this dissertation, we discuss several new methods and procedures which we have developed and used to produce OLEDs and PLEDs. More specifically these are electronic doping of transport layers, fluorescent doping of emissive layers by semiconductor nanocrystals (NC) (also known as quantum dots (QD)), and electrode engineering, namely by the use of transparent carbon nanotube sheets as charge injectors. We expand on the existing field of molecular doping and introduce a doped device with a very thick hole transport layer. Such a device is more resistant to failure due to excessive current density. We also investigate the effects of the presence of dopant molecules in the emissive layer of a multilayer OLED. This portion of the work introduces the negative

  20. Improved visible light photocatalytic activity of fluorine and nitrogen co-doped TiO2 with tunable nanoparticle size

    NASA Astrophysics Data System (ADS)

    Cheng, Junyang; Chen, Jin; Lin, Wei; Liu, Yandong; Kong, Yan

    2015-03-01

    Fluorine and nitrogen co-doped TiO2 (F-N-TiO2) photocatalysts with enhanced photocatalytic activities were facilely synthesized by a simple one-step hydrothermal method using Ti(SO4)2 as an economical precursor, and hydrofluoric acid and ammonia as F and N source, respectively. The structure, morphology, and optical properties of produced nanoparticles were characterized by X-ray diffraction (XRD), N2 adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectra (FT-IR) methods. The synergistic effects of F and N doping were systematically examined by changing the molar ratio of F/N. Compared with the un-doped F or N mono-doped TiO2, the co-doped samples exhibited significantly improved photocatalytic performance due to their synergistic effects under visible light. It was shown that F dopant promoted the crystal growth and crystallinity of samples, while N dopant hindered it to some extent, which resulted in the tunable particle size of obtained F-N-TiO2 materials. The effects of F and N dopants on the enhanced photocatalytic activity of modified TiO2 materials were also discussed. The degradation rate of methylene blue (MB) was achieved at 97.31% after 5 h reaction under visible light over the optimized sample of FN3.5T. The materials also showed excellent stability according to the recycling tests of the photodegradation of MB.

  1. Dual function of rare earth doped nano Bi2O3: white light emission and photocatalytic properties.

    PubMed

    Dutta, Dimple P; Roy, Mainak; Tyagi, A K

    2012-09-14

    Undoped Bi(2)O(3) and single and double doped Bi(2)O(3) : M (where M = Tb(3+) and Eu(3+)) nanophosphors were synthesized through a simple sonochemical process and characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), EDS, diffuse reflectance (DRS) and photoluminescence (PL) spectrophotometry. The TEM micrographs show that resultant nanoparticles have a rod-like shape. Energy transfer was observed from host to the dopant ions. Characteristic green emissions from Tb(3+) ions and red emissions from Eu(3+) ions were observed. Interestingly, the Commission International de l'Eclairage (CIE) coordinates of the double doped Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) nanorods lie in the white light region of the chromaticity diagram and it has a quantum efficiency of 51%. The undoped Bi(2)O(3) showed a band gap of 3.98 eV which is red shifted to 3.81eV in the case of double doped Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) nanorods. The photocatalytic activities of undoped nano Bi(2)O(3) and double doped nano Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) were evaluated for the degradation of Rhodamine B under UV irradiation of 310 nm. The results showed that Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) had better photocatalytic activity compared to undoped nano Bi(2)O(3). The evolution of CO(2) was realized and these results indicated the continuous mineralization of rhodamine B during the photocatalytic process. Thus double doped Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) nanorods can be termed as a bifunctional material exhibiting both photocatalytic properties and white light emission.

  2. Product selectivity of visible-light photocatalytic reduction of carbon dioxide using titanium dioxide doped by different nitrogen-sources

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaoguo; Huang, Zhengfeng; Cheng, Xudong; Wang, Qingli; Chen, Yi; Dong, Peimei; Zhang, Xiwen

    2015-11-01

    The influence of nitrogen-source on the photocatalytic properties of nitrogen-doped titanium dioxide is herein first investigated from the perspective of the chemical bond form of the nitrogen element in the nitrogen-source. The definitive role of groups such as Nsbnd N from the nitrogen-source on the surface of as-prepared samples in the selectivity of the dominant product of photocatalytic reduction is demonstrated. Well-crystallized one-dimensional Nsbnd TiO2 nanorod arrays with a preferred orientation of the rutile (3 1 0) facet are manufactured via a hydrothermal treatment using hydrazine and ammonia variously as the source of nitrogen. Significant selectivity of the dominant reduced products has been exhibited for Nsbnd TiO2 prepared from different nitrogen-sources in carbon dioxide photocatalytic reduction under visible light illumination. CH4 is the main product with N2H4-doped Nsbnd TiO2, while CO is the main product with NH3-doped Nsbnd TiO2, which can be attributed to the existence of the reducing Nsbnd N groups in the N2H4-doped Nsbnd TiO2 surfaces after the hydrothermal treatment. Compared with the approaches previously reported, the facile one-step route utilized here accomplishes the fabrication of Nsbnd TiO2 possessing visible-light activity and attainment of selectivity of dominant photocatalytic reduction product simultaneously by choosing a nitrogen-source with appropriate chemical bond form, which provides a completely new approach to understanding the effects of doping treatment on photocatalytic properties.

  3. Role of space charges on light-induced effects in nematic liquid crystals doped by methyl red.

    PubMed

    Lucchetti, L; Simoni, F

    2014-03-01

    We show that both the extraordinarily large nonlinear response and the light-induced permanent reorientation in liquid crystals doped by the azo dye methyl red originates from the same phenomenon of modification of the charge density on the irradiated surface. The demonstration is done by applying ac voltage to the samples, showing that in this case no permanent anchoring is possible. The measurements confirm the role of photoisomerization that gives a transient contribution to the actual reorientation process only in the high dose regime. This result allows us to draw a picture for light-induced effects that might be applied to a large class of compounds.

  4. Efficiency enhancement of InGaN/GaN light-emitting diodes with pin-doped GaN quantum barrier

    NASA Astrophysics Data System (ADS)

    Sirkeli, Vadim P.; Yilmazoglu, Oktay; Al-Daffaie, Shihab; Oprea, Ion; Ong, Duu Sheng; Küppers, Franko; Hartnagel, Hans L.

    2017-01-01

    Blue InGaN/GaN light-emitting diodes with undoped, heavily Si-doped, Si delta-doped, heavily Mg-doped, Mg delta-doped, and Mg-Si pin-doped GaN barrier are investigated numerically. The simulation results demonstrate that the Mg-Si pin-doping in the GaN barrier effectively reduces the polarization-induced electric field between the InGaN well and the GaN barrier in the multiple quantum well, suppresses the quantum-confined Stark effect, and enhances the hole injection and electron confinement in the active region. For this light-emitting diode (LED) device structure, we found that the turn-on voltage is 2.8 V, peak light emission is at 415.3 nm, and internal quantum efficiency is 85.9% at 100 A cm-2. It is established that the LED device with Mg-Si pin-doping in the GaN barrier has significantly improved efficiency and optical output power performance, and lower efficiency droop up to 400 A cm-2 compared with LED device structures with undoped or Si(Mg)-doped GaN barrier.

  5. Morphology-controlled synthesis of Ti{sup 3+} self-doped yolk–shell structure titanium oxide with superior photocatalytic activity under visible light

    SciTech Connect

    Wang, Shixiong; Yang, Xiangjun; Wang, Yapeng; Liu, Lixiang; Guo, Yuanyuan; Guo, Hong

    2014-05-01

    Ti{sup 3+} self-doped yolk–shell structure titanium oxide nanoparticle aggregates are fabricated through an environmental template-free route and the reduction reaction at low temperature subsequently. After the Ti{sup 3+} doping, the reduced TiO{sub 2} sample exhibits a wide visible-light absorption ranged from 400 nm to 800 nm. The intrinsic hollow core–shell microstructure can make multiple reflections of light within the chamber, and thus results in more efficient use of the light source compared with solid structure. Besides, the large surface area can render the sample with a high activity. Therefore, Ti{sup 3+} self-doped yolk–shell structure titanium oxide exhibits a superior photocatalytic activity under visible light. This strategy is simple, cheap and mass-productive, which may shed light on a new avenue for large scale production of self-doped yolk–shell structural nano functional materials for catalyst, sensors, energy storage and other new applications. - Graphical abstract: A facile generic strategy is employed to prepare Ti{sup 3+} self-doped yolk–shell structure titanium oxide nanoparticle aggregates with the superior photocatalytic activity under visible light. - Highlights: • Yolk–shell TiO{sub 2} mesospheres are synthesized by solvothermal alcoholysis. • Ti{sup 3+} self-doped yolk–shell structure titanium oxide is obtained at low temperature. • It exhibits a remarkable photocatalytic activity.

  6. Enhanced visible-light response of metal-free doped bulk h-BN as potential efficient photocatalyst: a computational study.

    PubMed

    Wang, Fang; Cao, Yuehan; Wei, Shiqian; Zhou, Ying

    2017-01-01

    We have provided a straightforward route to screen a series of metal-free doped bulk h-BN as potential visible-light photocatalysts via the first-principle computations. Various nonmetal dopants are considered including Si, P, C, S, Cl, O, and F atoms according to increasing electronegativity. The results show that the introduction of nonmetals leads to small lattice distortions but significant modifications of band structures, electron transition paths and chemical bonding interactions. Generally, all doped h-BN except Si doping have an active response to the visible-light, and dopants with higher electronegativity can significantly narrow the band gaps, which could induce easier optical transition under visible-light excitation. Based on the electronic structures and absorption spectra, three different mechanisms of enhanced visible-light response for the doping effect are proposed. It is expected that F, Cl, and S-doped h-BN could be used as potential efficient visible-light driven photocatalysts. This study could aid in the design of novel efficient h-BN photocatalysts. Graphical Abstract The mechanisms of the enhanced visible-light response of metal-free doped bulk h-BN.

  7. Efficiency droop enhancement in AlGaN deep ultraviolet light-emitting diodes by making whole barriers but the bottom Mg doped

    NASA Astrophysics Data System (ADS)

    Sun, Jie; Sun, Huiqing; Yi, Xinyan; Yang, Xian; Fan, Xuancong; Zhang, Cheng; Zhang, Zhuding; Guo, Zhiyou

    2016-09-01

    Ultra violet light-emitting diodes (UVLEDs) with different types of Mg-doped barriers have been studied. The energy band diagrams, internal quantum efficiency, total output power and radiative recombination rate are investigated by APSYS software. The simulation results show that the UVLED with only a p-doped top barrier get little enhancement comparing to the conventional one, on the contrary the structure with p-doping in all but the bottom barriers has a much better optical and electrical properties due to enhancement of the holes' injection and the electrons' confinement. The efficiency droop is significantly alleviated and the light output power is greatly enhanced. To avoid forming a PN junction by the bottom barrier and the n-AlGaN in the proposed structure, therefore, the bottom barrier isn't p-doped. Then structures with different hole densities in the Mg-doped barriers have been studied numerically and that confirmed the best.

  8. Photocatalytic hydrogen generation over lanthanum doped TiO2 under UV light irradiation.

    PubMed

    Liu, Y; Xie, L; Li, Y; Qu, J L; Zheng, J; Li, X G

    2009-02-01

    TiO2 nanoparticles doped with different amount of lanthanum were obtained by sol-gel approach and followed annealing at different temperature. The crystal size of TiO2 doped with lanthanum was smaller than that of pure TiO2. Photocatalytic activity of TiO2 doped with lanthanum for water splitting into H2 was investigated. The photocatalytic activity of TiO2 doped with lanthanum for water splitting into H2 is higher than that of pure TiO2. It was found that the optimal photocatalyst was TiO2 doped with 2 wt% lanthanum and calcined at 600 degrees C for 4 h which had hydrogen generation rate 700.6 micromol h(-1).

  9. Polarization induced doped transistor

    SciTech Connect

    Xing, Huili; Jena, Debdeep; Nomoto, Kazuki; Song, Bo; Zhu, Mingda; Hu, Zongyang

    2016-06-07

    A nitride-based field effect transistor (FET) comprises a compositionally graded and polarization induced doped p-layer underlying at least one gate contact and a compositionally graded and doped n-channel underlying a source contact. The n-channel is converted from the p-layer to the n-channel by ion implantation, a buffer underlies the doped p-layer and the n-channel, and a drain underlies the buffer.

  10. Organic light emitting field effect transistors based on an ambipolar p-i-n layered structure

    NASA Astrophysics Data System (ADS)

    Maiorano, V.; Bramanti, A.; Carallo, S.; Cingolani, R.; Gigli, G.

    2010-03-01

    A bottom contact/top gate ambipolar "p-i-n" layered light emitting field effect transistor with the active medium inserted between two doped transport layers, is reported. The doping profile results crucial to the capability of emitting light, as well as to the electrical characteristics of the device. In this sense, high output current at relative low applied gate/drain voltage and light emission along the whole large area transistor channel are observed, putting the basis to full integration of organic light emitting field effect transistors in planar complex devices.

  11. Effects of ultraviolet light on B-doped CdS thin films prepared by spray pyrolysis method using perfume atomizer

    NASA Astrophysics Data System (ADS)

    Novruzov, V. D.; Keskenler, E. F.; Tomakin, M.; Kahraman, S.; Gorur, O.

    2013-09-01

    Boron doped CdS thin films were deposited by spray pyrolysis method using perfume atomizer. The effects of ultraviolet light on the structural, optical and electrical properties of B-doped CdS thin films were investigated as a function of dopant concentration (B/Cd). X-ray diffraction studies showed that all samples were polycrystalline nature with hexagonal structure. It was determined that the preferred orientation of non-illuminated samples changes from (1 0 1) to (0 0 2) with B concentration. The c lattice constant of films decreases from 6.810 Å to 6.661 Å with boron doping. The XRD peak intensity increased with the illumination for almost all the samples. The lattice parameters of B-doped samples remained nearly constant after illumination. It was found that the optical transmittance, photoluminescence spectra, resistivity and carrier concentration of the B-doped samples are stable after the illumination with UV light. Also the effects of UV light on B-doped CdS/Cu2S solar cell were investigated and it was determined that photoelectrical parameters of B-doped solar cell were more durable against the UV light.

  12. Effects of doping amounts of potassium ferricyanide with titanium dioxide and calcination durations on visible-light degradation of pharmaceuticals.

    PubMed

    Lin, Justin Chun-Te; de Luna, Mark Daniel G; Gotostos, Mary Jane N; Lu, Ming-Chun

    2016-11-01

    Acetaminophen (ACT) is one of the most frequently detected pharmaceuticals in aqueous environments, and treatment of ACT were generally carried out by photocatalytic degradations under high energy UV irradiation. In this study, potassium ferricyanide was utilized as a quadruple-elemental dopant in a TiO2 photocatalyst in order to enhance its visible-light activity. Two critical parameters (amounts of dopants and durations of calcination) of the synthesis of the photocatalyst by a sol-gel method were systematically evaluated. Crystal structure of the doping TiO2 was examined by X-ray diffraction while the effects of the two parameters on the photocatalytic activity were elucidated by various characterizations. Increasing the amount of dopant or the duration of calcination red-shifted the UV-vis DRS of the doped TiO2. The estimated band gap energy of the doped TiO2 decreased slightly as the amount of dopant increased, but it increased as the duration of calcination increased. The FT-IR yielded characteristic peaks that revealed the effects of the two parameters, whereas the SEM images revealed the morphological evolutions of each effect. The photocatalyst, synthesized at optimum conditions was able to remove 99.1 % acetaminophen with rate constant of 7.9 × 10(-3) min(-1), which was 4.88 times greater than virgin TiO2. In general, this study not only optimized synthetic conditions of the new visible-light active photocatalyst for ACT degradation but also presented characterizations conducted by SEM, XRD, UV-vis DRS, and FTIR to elucidate the relationship between modified structure and the photocatalytic activity. Graphical abstract Effects of doping amounts of K3[Fe(CN)6] and calcunation duration on visible light absorbance of TiO2 photocatalysts.

  13. Synthesis and characterization of samarium-doped ZnS nanoparticles: A novel visible light responsive photocatalyst

    SciTech Connect

    Hanifehpour, Younes; Soltani, Behzad; Amani-Ghadim, Ali Reza; Hedayati, Behnam; Khomami, Bamin; Joo, Sang Woo

    2016-04-15

    Highlights: • Sm-doped ZnS Nanomaterials were synthesized by hydrothermal method. • The as-prepared compounds were characterized by XRD, TEM, XPS, SEM and UV techniques. • The photocatalytic effect of compounds was determined by Reactive Red 43 degradation. • The degradation of RRed 43 followed the Langmuir–Hinshelwood kinetic model. - Abstract: We prepared pure and samarium-doped ZnS (Sm{sub x}Zn{sub 1−x}S{sub 1+0.5x}) nanoparticles via hydrothermal process at 160 °C for 24 h. XRD analysis shows that the particles were well crystallized and corresponds to a cubic sphalerite phase. SEM and TEM images indicate that the sizes of the particles were in the range of 20–60 nm. The photocatalytic activity of Sm-doped ZnS nanoparticles was evaluated by monitoring the decolorization of Reactive Red 43 in aqueous solution under visible light irradiation. The color removal efficiency of Sm{sub 0.04}Zn{sub 0.96}S and pure ZnS was 95.1% and 28.7% after 120 min of treatment, respectively. Among the different amounts of dopant agent used, 4% Sm-doped ZnS nanoparticles indicated the highest decolorization. We found that the presence of inorganic ions such as Cl{sup −}, CO{sub 3}{sup 2−} and other radical scavengers such as buthanol and isopropyl alcohol reduced the decolorization efficiency.

  14. Important role of surface fluoride in nitrogen-doped TiO2 nanoparticles with visible light photocatalytic activity.

    PubMed

    Brauer, Jonathan I; Szulczewski, Greg

    2014-12-11

    Nitrogen-doped TiO2 nanoparticles have been synthesized using sol-gel methods and subsequently fluorinated at room temperature by aging in acidic solutions of NaF. The nanoparticles were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, UV-vis, and IR diffuse reflectance spectroscopy. After aging at room temperature in NaF solutions, the Ti-OH groups on the surface of the TiO2 nanoparticles were replaced by Ti-F bonds, which resulted in a decrease of the point of zero charge from pH 5.4 to 2.8. Most importantly, the nitrogen dopants were retained after the fluorination process, and the amorphous nanoparticles were partially converted into the anatase phase. Annealing the photocatalysts resulted in a decrease of both the nitrogen and fluoride atomic concentration. Diffuse reflectance spectra show an increase in absorbance above 400 nm after annealing the F,N-doped TiO2, which suggests the formation of color centers. The photoactivity of the F,N-doped and N-doped TiO2 catalysts were evaluated by monitoring by the decolorization of methylene blue with visible light. Mass spectrometric analysis revealed that methylene blue undergoes successive demethylation, and more importantly, the rate of decolorization depends on the fluoride concentration. These results show the importance of a two-step synthesis method to independently control the nitrogen and fluoride concentration.

  15. Ce Core-Level Spectroscopy, and Magnetic and Electrical Transport Properties of Lightly Ce-Doped YCoO3

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yoshihiko; Koike, Tsuyoshi; Okawa, Mario; Takayanagi, Ryohei; Takei, Shohei; Minohara, Makoto; Kobayashi, Masaki; Horiba, Koji; Kumigashira, Hiroshi; Yasui, Akira; Ikenaga, Eiji; Saitoh, Tomohiko; Asai, Kichizo

    2016-11-01

    We have investigated the Ce and Co core level spectroscopy, and the magnetic and electrical transport properties of lightly Ce-doped YCoO3. We have successfully synthesized single-phase Y1-xCexCoO3 for 0.0 ≤ x ≤ 0.1 by the sol-gel method. Hard X-ray photoelectron and X-ray absorption spectroscopy experiments reveal that the introduced Ce ions are tetravalent, which is considered to be the first case of electron doping into bulk trivalent Co oxides with perovskite RECoO3 (RE: rare-earth element or Y) caused by RE site substitution. The magnitude of the effective magnetic moment peff obtained from the temperature dependence of magnetic susceptibility χ(T) at higher temperatures is close to that for high-spin Co2+ introduced by the Ce doping, implying that the electrons doped into the Co site induce Co2+ with a high-spin state. For x = 0.1, ferromagnetic ordering is observed below about 7 K. Electrical transport properties such as resistivity and thermoelectric power show that negative electron-like carriers are introduced by Ce substitution.

  16. Synthesis of porous carbon-doped g-C3N4 nanosheets with enhanced visible-light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Bao, Nan; Hu, Xinde; Zhang, Qingzhe; Miao, Xinhan; Jie, Xiuyan; Zhou, Shuai

    2017-05-01

    The porous carbon-doped g-C3N4 nanosheets photocatalysts (NSs-APAM) were synthesized using anionic polyacrylamide (APAM) as the intercalator and carbon source via the thermal treatment method. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance absorption spectra (UV-DRS) and photoluminescence spectroscopy (PL). The results indicate that the APAM can effectively induce the formation of high-quality nanosheets (NSs) with narrowed bandgap. The specific surface area of NSs-APAM is 118.6 m2/g, which is 5-fold larger than bulk g-C3N4. The carbon doping could narrow the bandgap, from 2.75 eV of g-C3N4 NSs without carbon doping (NSs-Water) to 2.41 eV of NSs-APAM. The two-dimensional NSs structure facilitates the charge separation by shortening the diffusion distance to the surface of photocatalysts. The synergic effects of the carbon doping and unique structural properties contributed to the superior photocatalytic activity of NSs-APAM with 95% degradation rate towards X-3 B after 30 min visible-light irradiation.

  17. SU-E-T-782: Using Light Output From Doped Plastic Scintillators to Resolve the Linear Energy Transfer Spectrum of Clinical Electron Beams

    SciTech Connect

    Nusrat, H; Pang, G; Ahmad, S; Keller, B; Sarfehnia, A

    2015-06-15

    Purpose: This research seeks to develop a portable, clinically-suitable linear energy transfer (LET) detector. In radiotherapy, absorbed dose is commonly used to measure the amount of delivered radiation, though, it is not a good indicator of actual biological damage. LET is the energy absorbed per unit length by a medium along charged particle’s pathway; studies have shown that LET correlates well with relative biological effectiveness (RBE). Methods: According to Birks’ law, light output of plastic scintillators is stopping-power dependent. This dependency can be varied through doping by various high-Z elements. By measuring light output signals of differently doped plastic scintillators (represented by column vector S, where each row corresponds to different scintillator material), the fluence of charged particles of a given LET (represented by column vector Φ, where each row corresponds to different LET bins) can be unfolded by S=R*Φ where R is system response matrix (each row represents a different scintillator, each column corresponds to different electron LET). Monte Carlo (MC) GEANT4.10.1 was used to evaluate ideal detector response of BC408 scintillating material doped with various concentrations of several high Z dopants. Measurements were performed to validate MC. Results: Signal for 1%-lead doped BC408 and the non-doped scintillator was measured experimentally by guiding light emitted by the scintillator (via in-house made taper, fiber system) to a PMT and then an electrometer. Simulations of 1%Pb-doped scintillator to non-doped scintillator revealed 9.3% reduction in light output for 6 MeV electrons which compared well (within uncertainty) with measurements showing 10% reduction (6MeV electrons). Conclusion: Measurements were used to validate MC simulation of light output from doped scintillators. The doping of scintillators is a viable technique to induce LET dependence. Our goal is to use this effect to resolve the LET spectrum of an incident

  18. Transition-metal-doped ZnO nanoparticles: synthesis, characterization and photocatalytic activity under UV light.

    PubMed

    Saleh, Rosari; Djaja, Nadia Febiana

    2014-09-15

    ZnO nanoparticles doped with transition metals (Mn and Co) were prepared by a co-precipitation method. The synthesized nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-rays, Fourier transform infrared spectroscopy, electron spin resonance spectroscopy and diffuse reflectance spectroscopy. The photocatalytic activities of the transition-metal-doped ZnO nanoparticles were evaluated in the degradation of methyl orange under UV irradiation. ZnO nanoparticles doped with 12 at.% of Mn and Co ions exhibited the maximum photodegradation efficiency. The experiment also demonstrated that the photodegradation efficiency of Mn-doped ZnO nanoparticles was higher than that of Co-doped ZnO nanoparticles. These results indicate that charge trapping states due to the doping were the decisive factor rather than the average particle size and energy gap. Moreover the effect of pH values on the degradation efficiency was discussed in the photocatalytic experiments using 12 at.% Mn- and Co-doped ZnO nanoparticles.

  19. Transition-metal-doped ZnO nanoparticles: Synthesis, characterization and photocatalytic activity under UV light

    NASA Astrophysics Data System (ADS)

    Saleh, Rosari; Djaja, Nadia Febiana

    2014-09-01

    ZnO nanoparticles doped with transition metals (Mn and Co) were prepared by a co-precipitation method. The synthesized nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-rays, Fourier transform infrared spectroscopy, electron spin resonance spectroscopy and diffuse reflectance spectroscopy. The photocatalytic activities of the transition-metal-doped ZnO nanoparticles were evaluated in the degradation of methyl orange under UV irradiation. ZnO nanoparticles doped with 12 at.% of Mn and Co ions exhibited the maximum photodegradation efficiency. The experiment also demonstrated that the photodegradation efficiency of Mn-doped ZnO nanoparticles was higher than that of Co-doped ZnO nanoparticles. These results indicate that charge trapping states due to the doping were the decisive factor rather than the average particle size and energy gap. Moreover the effect of pH values on the degradation efficiency was discussed in the photocatalytic experiments using 12 at.% Mn- and Co-doped ZnO nanoparticles.

  20. Dramatic activities of vanadate intercalated bismuth doped LDH for solar light photocatalysis.

    PubMed

    Mohapatra, Lagnamayee; Parida, K M

    2014-08-28

    To harvest solar energy efficiently, a series of Zn/Bi layered double hydroxide (LDH) photocatalysts with different molar ratios of Zn/Bi (2 : 1, 3 : 1, 4 : 1) has been synthesized by a coprecipitation method at constant pH. All the Bi doped LDH samples displayed hydrotalcite-like structure with interlayer carbonate, in which crystallinity decreases as the bismuth content increases. The Zn/Bi (4 : 1) LDH with a small amount of bismuth in the brucite layer and possessing high crystallinity was further modified hydrothermally by intercalating decavanadate and it showed high photochemical stability and photocatalytic activity for the degradation of different organic pollutants for practical applications under solar light irradiation. The structural integrity of the materials has been successfully characterized by studying their structural, morphological, electronic and optical properties by various physico-chemical techniques. The present study provided an insight into oxo-bridged MMCT of the LDH and established that the Zn(II)-O-Bi(III) units resulted in the generation of superoxide radicals which is clearly observed by the EPR technique. The ˙OH radicals formed during photocatalysis were revealed by means of the terephthalic acid fluorescence probe method. The photoelectrochemical measurement confirmed that the intercalated vanadate anion was crucial to obtain an optimal synergistic effect for the degradation of organic pollutants. The prolonged lifetime of photogenerated charges and improved charge transfer capability were confirmed by time-resolved fluorescence emission spectra. Furthermore, a detailed mechanism for the enhanced photocatalytic activity was discussed.

  1. A visible light response TiO2 photocatalyst realized by cationic S-doping and its application for phenol degradation.

    PubMed

    Liu, Shouxin; Chen, Xiaoyun

    2008-03-21

    S-doped TiO2 photocatalyst with high visible light activity was prepared by acid catalyzed hydrolysis method using thiourea (TU) as sulfur source. The catalyst was characterized by DRS, XPS, XRD, FTIR, SEM and N2 adsorption. It was found that cation S6+ was homogeneously incorporated into the bulk phase of TiO2 and substitutes for some of the lattice titanium (Ti4+). Doped S can form a new band above the valence band and narrow the band-gap of the photocatalyst, giving rise to a second absorption edge in the visible light region. The activity of the catalyst was examined by photodegradation of phenol in aqueous solution under both artificial visible light and solar light irradiation. The activity of catalyst was found to be dependent on the doping amount of S and the maximum activity was observed when the catalyst was obtained by calcinated at 600 degrees C with the mass ratio of TU/TiO2=1. Too much of new-generated band-gap structures due to higher S-doping could act as recombination centers for electron-hole pairs. Catalyst with optimum S-doping exhibited the highest activity under both artificial light and solar irradiation for phenol degradation. In addition, doped S also beneficial for the better dispersion, large S(BET) and phase transformation retardation of TiO2.

  2. Light-induced relaxation dynamics in Rh-doped Bi12TiO20 crystals

    NASA Astrophysics Data System (ADS)

    Marinova, V.; Vlaikova, E.; Goovaerts, E.

    2014-12-01

    The lifetime of the excited charge carriers in Rh-doped BTO crystals is characterized by measuring the time-resolved photoinduced absorption (PIA) after nanosecond pulse excitation from a frequency doubled Nd:YAG laser (λ=532 nm). It was found that the Rh-addition in the BTO structure slows down the relaxation decay in comparison with non- doped BTO, which is attributed to additional trapping centers related to the rhodium dopant. The experimental curve is well fitted by a double-exponential decay which is ascribed to the presence of two different shallow traps contributing to the charge transport and recombination mechanisms in Rh-doped BTO crystal.

  3. Visible light photocatalytic property of Zn doped V2O5 nanoparticles

    NASA Astrophysics Data System (ADS)

    Suresh, R.; Giribabu, K.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2012-06-01

    The Zn doped V2O5 nanoparticles were synthesized by thermal decomposition method. The prepared samples were characterized by various techniques like Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) studies, UV-Visible spectroscopy (UV-Vis) and field emission scanning electron microscopy (FE-SEM). The photocatalytic activities of pure and Zn doped V2O5 nanoparticles were examined based on the photodegradation of Rhodamine B (RhB). Experimental results indicated that the Zn doped V2O5 photocatalyst (the molar ratio of V to Zn is 99: 1) exhibited maximum photocatalytic activity.

  4. Rhodium-doped barium titanate perovskite as a stable p-type semiconductor photocatalyst for hydrogen evolution under visible light.

    PubMed

    Maeda, Kazuhiko

    2014-02-12

    Rhodium-doped barium titanate (BaTiO3:Rh) powder was prepared by the polymerized complex (PC) method, and the photocatalytic activity for H2 evolution from water was examined. BaTiO3 is a wide-gap n-type semiconductor having a band gap of 3.0 eV. Doping Rh species into the lattice of BaTiO3 resulted in the formation of new absorption bands in visible light region. Upon visible light (λ > 420 nm), BaTiO3:Rh modified with nanoparticulate Pt as a water reduction promoter was capable of producing H2 from water containing an electron donor such as methanol and iodide. The best material prepared by the PC method exhibited higher activity than that made by a conventional solid-state reaction method. Visible-light-driven Z-scheme water splitting was also accomplished using Pt/BaTiO3:Rh as a building block for H2 evolution in combination with PtOx-loaded WO3 as an O2 evolution photocatalyst in the presence of an IO3(-)/I(-) shuttle redox mediator. Photoelectrochemical analysis indicated that a porous BaTiO3:Rh electrode exhibited cathodic photoresponse due to water reduction in a neutral aqueous Na2SO4 solution upon visible light.

  5. White light generation in Tb3+/Eu3+/Dy3+ triply-doped Zn(PO3)2 glass

    NASA Astrophysics Data System (ADS)

    Meza-Rocha, A. N.; Lozada-Morales, R.; Speghini, A.; Bettinelli, M.; Caldiño, U.

    2016-01-01

    A spectroscopic investigation of Tb3+/Eu3+/Dy3+ triply-doped Zn(PO3)2 glass focused on generation of white light is performed through photoluminescence spectra and decay time measurements. The white light emission obtained in the glass phosphor shows excitation wavelength dependent tunable tonality: neutral white (0.385, 0.441) of 4250 K and warm white (0.417, 0.412) of 3429 K, upon 445 and 322 nm excitations, respectively. A quantum yield of 26.1 ± 1.2% is attained upon Dy3+ excitation at 445 nm. The white luminescence is due mainly to terbium 5D4 → 7F5, dysprosium 4F9/2 → 6H15/2,13/2 and europium 5D0 → 7F2 transitions. It is demonstrated that non-radiative energy transfers Dy3+ to Tb3+ and Eu3+, and Tb3+ to Eu3+, take place in the glass phosphor excited at 445 or 322 nm. Tb3+/Eu3+/Dy3+ triply-doped Zn(PO3)2 glass, excited by AlGaN (322 nm) or InGaN (445 nm) LEDs, could then be appropriated for solid state lighting technology as neutral or warm white light phosphors.

  6. Electronic structure and visible light photocatalysis water splitting property of chromium-doped SrTiO{sub 3}

    SciTech Connect

    Liu, J.W.; Chen, G. . E-mail: gchen@hit.edu.cn; Li, Z.H.; Zhang, Z.G.

    2006-12-15

    Cr-doped SrTi{sub 1-} {sub x} Cr {sub x} O{sub 3} (x=0.00, 0.02, 0.05, 0.10) powders, prepared by solvothermal method, were further characterized by ultraviolet-visible (UV-vis) absorption spectroscopy. The UV-vis spectra indicate that the SrTi{sub 1-} {sub x} Cr {sub x} O{sub 3} powders can absorb not only UV light like pure SrTiO{sub 3} powder but also the visible-light spectrum ({lambda}>420 nm). The results of density functional theory (DFT) calculation illuminate that the visible-light absorption bands in the SrTi{sub 1-} {sub x} Cr {sub x} O{sub 3} catalyst are attributed to the band transition from the Cr 3d to the Cr 3d+Ti 3d hybrid orbital. The photocatalytic activities of chromium-doped SrTiO{sub 3} both under UV and visible light are increased with the increase in the amounts of chromium. -- Graphical abstract: SrTi{sub 1-} {sub x} Cr {sub x} O{sub 3} powders, prepared by solvothermal method, can absorb not only UV light like pure SrTiO{sub 3} powder but also the visible-light spectrum ({lambda}>420 nm). The results of DFT calculation illuminate that the visible-light absorption bands in the SrTi{sub 1-} {sub x} Cr {sub x} O{sub 3} catalyst are attributed to the band transition from the Cr 3d to the Cr 3d+Ti 3d hybrid orbital.

  7. Room temperature synthesis of Mn{sup 2+} doped ZnS d-dots and observation of tunable dual emission: Effects of doping concentration, temperature, and ultraviolet light illumination

    SciTech Connect

    Kole, A. K.; Kumbhakar, P.; Tiwary, C. S.

    2013-03-21

    Mn{sup 2+} doped (0-50.0 molar %) ZnS d-dots have been synthesized in water medium by using an environment friendly low cost chemical technique. Tunable dual emission in UV and yellow-orange regions is achieved by tailoring the Mn{sup 2+} doping concentration in the host ZnS nanocrystal. The optimum doping concentration for achieving efficient photoluminescence (PL) emission is determined to be {approx}1.10 (at. %) corresponding to 40.0 (molar %) of Mn{sup 2+} doping concentration used during synthesis. The mechanism of charge transfer from the host to the dopant leading to the intensity modulated tunable (594-610 nm) yellow-orange PL emission is straightforwardly understood as no capping agent is used. The temperature dependent PL emission measurements are carried out, viz., in 1.10 at. % Mn{sup 2+} doped sample and the experimental results are explained by using a theoretical PL emission model. It is found that the ratio of non-radiative to radiative recombination rates is temperature dependent and this phenomenon has not been reported, so far, in Mn{sup 2+} doped ZnS system. The colour tuning of the emitted light from the samples are evident from the calculated chromaticity coordinates. UV light irradiation for 150 min in 40.0 (molar %) Mn{sup 2+} doped sample shows an enhancement of 33% in PL emission intensity.

  8. Synthesis, characterization and photocatalytic evaluation of visible light activated C-doped TiO2 nanoparticles.

    PubMed

    Liu, Guanglong; Han, Changseok; Pelaez, Miguel; Zhu, Duanwei; Liao, Shuijiao; Likodimos, Vlassis; Ioannidis, Nikolaos; Kontos, Athanassios G; Falaras, Polycarpos; Dunlop, Patrick S M; Byrne, J Anthony; Dionysiou, Dionysios D

    2012-07-27

    We have demonstrated heterogeneous photocatalytic degradation of microcystin-LR (MC-LR) by visible light activated carbon doped TiO(2) (C-TiO(2)) nanoparticles, synthesized by a modified sol-gel route based on the self-assembly technique exploiting oleic acid as a pore directing agent and carbon source. The C-TiO(2) nanoparticles crystallize in anatase phase despite the low calcination temperature of 350 °C and exhibit a highly porous structure that can be optimized by tuning the concentration of the oleic acid surfactant. The carbon modified nanomaterials exhibited enhanced absorption in the broad visible light region together with an apparent red shift in the optical absorption edge by 0.5 eV (2.69 eV), compared to the 3.18 eV of reference anatase TiO(2). Carbon species were identified by x-ray photoelectron spectroscopy analysis through the formation of both Ti-C and C-O bonds, indicative of substitution of carbon for oxygen atoms and the formation of carbonates, respectively. Electron paramagnetic resonance spectroscopy revealed the formation of two carbon related paramagnetic centers in C-TiO(2), whose intensity was markedly enhanced under visible light illumination, pointing to the formation of localized states within the anatase band gap, following carbon doping. The photocatalytic activity of C-TiO(2) nanomaterials was evaluated for the degradation of MC-LR at pH 3.0 under visible light (λ > 420 nm) irradiation. The doped materials showed a higher MC-LR degradation rate than reference TiO(2), behavior that is attributed to the incorporation of carbon into the titania lattice.

  9. Synthesis, characterization and photocatalytic evaluation of visible light activated C-doped TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Guanglong; Han, Changseok; Pelaez, Miguel; Zhu, Duanwei; Liao, Shuijiao; Likodimos, Vlassis; Ioannidis, Nikolaos; Kontos, Athanassios G.; Falaras, Polycarpos; Dunlop, Patrick S. M.; Byrne, J. Anthony; Dionysiou, Dionysios D.

    2012-07-01

    We have demonstrated heterogeneous photocatalytic degradation of microcystin-LR (MC-LR) by visible light activated carbon doped TiO2 (C-TiO2) nanoparticles, synthesized by a modified sol-gel route based on the self-assembly technique exploiting oleic acid as a pore directing agent and carbon source. The C-TiO2 nanoparticles crystallize in anatase phase despite the low calcination temperature of 350 °C and exhibit a highly porous structure that can be optimized by tuning the concentration of the oleic acid surfactant. The carbon modified nanomaterials exhibited enhanced absorption in the broad visible light region together with an apparent red shift in the optical absorption edge by 0.5 eV (2.69 eV), compared to the 3.18 eV of reference anatase TiO2. Carbon species were identified by x-ray photoelectron spectroscopy analysis through the formation of both Ti-C and C-O bonds, indicative of substitution of carbon for oxygen atoms and the formation of carbonates, respectively. Electron paramagnetic resonance spectroscopy revealed the formation of two carbon related paramagnetic centers in C-TiO2, whose intensity was markedly enhanced under visible light illumination, pointing to the formation of localized states within the anatase band gap, following carbon doping. The photocatalytic activity of C-TiO2 nanomaterials was evaluated for the degradation of MC-LR at pH 3.0 under visible light (λ > 420 nm) irradiation. The doped materials showed a higher MC-LR degradation rate than reference TiO2, behavior that is attributed to the incorporation of carbon into the titania lattice.

  10. Decoloration of organic dyes using zeolites supported Fe-doped ZnO under UV light irradiation

    NASA Astrophysics Data System (ADS)

    Pratiwi, M. I.; Afifah, N.; Saleh, R.

    2017-07-01

    Various weight percentages of natural zeolite (10 % - 40 %) had been coupled into Fe-doped ZnO (Fe:ZnO) nanoparticles using the co-precipitation method. The photocatalytic acivity of Fe:ZnO/Zeolites nanocomposites was monitored under UV light irradiation in decoloring methylene blue and methyl orange. The result shows that certain amount of natural zeolite in Fe:ZnO could increase the photocatalytic activity of the nanocomposites. The synthesized samples were characterized using some measurements such as Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and Brunauer-Emment-Tellet (BET) surface area analysis. The FTIR spectra of the samples show the existance of zeolites in the samples. XRD patterns show that no crystal structure changes in ZnO after doping with Fe and supported with zeolites.

  11. Ultraviolet emission from Sb-doped p-type ZnO based heterojunction light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Mandalapu, L. J.; Yang, Z.; Chu, S.; Liu, J. L.

    2008-03-01

    Heterojunction light emitting diodes (LEDs) were fabricated by making Au /Ni top Ohmic contacts on Sb-doped p-type ZnO film with low specific contact resistivity and Al /Ti back Ohmic contacts on n-type Si substrate. Near-band edge and deep-level emissions were observed from the LED devices at both low temperatures and room temperature, which is due to band-to-band and band-to-deep level radiative recombinations in ZnO, respectively. The electroluminescence emissions precisely match those of photoluminescence spectra from Sb-doped p-type ZnO, indicating that the ZnO layer acts as the active region for the radiative recombinations of electrons and holes in the diode operation.

  12. Antibacterial activities of Nd doped and Ag coated TiO2 nanoparticles under solar light irradiation.

    PubMed

    Bokare, Anuja; Sanap, Avinash; Pai, Mrinal; Sabharwal, Sushma; Athawale, Anjali A

    2013-02-01

    Nanosized (8-9 nm) Nd doped and Ag coated TiO(2) nanoparticles have been synthesized by sol-gel method. The physicochemical properties of these particles were investigated by X-ray diffraction (XRD), diffuse reflectance UV-visible (DRUV) spectra and Brunauer-Emmett-Teller (BET) surface area analysis. The antibacterial activities of the samples were studied for Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) both, under the light and dark conditions. The results reveal that the extent of activity shows the order as undoped TiO(2)doped TiO(2)

  13. Ultraviolet emission from Sb-doped p-type ZnO based heterojunction light-emitting diodes

    SciTech Connect

    Mandalapu, L. J.; Yang, Z.; Chu, S.; Liu, J. L.

    2008-03-24

    Heterojunction light emitting diodes (LEDs) were fabricated by making Au/Ni top Ohmic contacts on Sb-doped p-type ZnO film with low specific contact resistivity and Al/Ti back Ohmic contacts on n-type Si substrate. Near-band edge and deep-level emissions were observed from the LED devices at both low temperatures and room temperature, which is due to band-to-band and band-to-deep level radiative recombinations in ZnO, respectively. The electroluminescence emissions precisely match those of photoluminescence spectra from Sb-doped p-type ZnO, indicating that the ZnO layer acts as the active region for the radiative recombinations of electrons and holes in the diode operation.

  14. Ultraviolet-driven white light generation from oxyfluoride glass co-doped with Tm3+-Tb3+-Eu3+

    NASA Astrophysics Data System (ADS)

    Kuznetsov, A. S.; Nikitin, A.; Tikhomirov, V. K.; Shestakov, M. V.; Moshchalkov, V. V.

    2013-04-01

    Tm3+-Tb3+-Eu3+ co-doped oxyfluoride glasses, doped with about 3.0 mol. % TmF3, 0.25 mol. % TbF3, and 0.25 mol. % EuF3, have been prepared by melt quenching technique. Under excitation at commercial 365 nm, the rare-earth co-dopants are all directly excited and emit in the blue, green, and red, respectively, without appreciable energy transfer amongst the co-dopants. Tint of the white luminescence can be adjusted by changing the ratio of the co-dopants. Properties of the glass host promote excellent dissolution of the co-dopants and low non-radiative decay rate. The white emission at 365 nm excitation is suitable for light emitting diodes applications.

  15. Time dependent diffraction ring patterns in bromothymol blue dye doped PMMA film under irradiation with continuous wave green laser light

    NASA Astrophysics Data System (ADS)

    Al-Saymari, F. A.; Badran, H. A.; Al-Ahmad, A. Y.; Emshary, C. A.

    2013-11-01

    Diffraction ring patterns are generated in bromothymol blue (BTB) doped poly methyl methacrylate (PMMA) film with the aid of visible light from a solid state laser of Gaussian distribution. Temporal evolution of patterns i.e. the number of rings increases as time elapse is observed. Based on the experimental findings, change in refractive index ( ∆n) effective nonlinear refractive index ( n 2) and variation of refractive index with temperature ( dn/ dT) have been obtained as 0.0025, 1.45 × 10-6 cm2 W-1, 1.69 × 10-5 K-1 respectively. Obtained results suggest the possibility of using BTB doped PMMA in data storage, recording and holography.

  16. Improved characteristics of organic light-emitting devices by surface modification of nickel-doped indium tin oxide anode

    SciTech Connect

    Hsu, C.-M.; Wu, W.-T.

    2004-08-02

    This letter presents the optoelectrical performance of an organic light-emitting diode (OLED) through the elevation of indium tin oxide (ITO) anode work function by Ni co-sputter surface doping and additional O{sub 2} plasma treatment. The turn-on voltage of OLED devices can be reduced by 2.3 V for Ni atomic concentration greater than 1.8% and by 2.7 V for the additional O{sub 2} plasma treatment. Devices with Ni(2.6%)-doped and O{sub 2} plasma treated ITO anodes perform the highest luminance efficiency (0.91 lm/W), three times larger than undoped ITO (0.31 lm/W) at 250 cd/m{sup 2}.

  17. Efficient inverted organic light-emitting devices with self or intentionally Ag-doped interlayer modified cathode

    SciTech Connect

    Liu, Wenbo; Liu, Shihao; Yu, Jing; Zhang, Wei; Wen, Xuemei; Yin, Yongming; Zhang, Letian; Chen, Ping; Xie, Wenfa

    2014-03-03

    Green phosphorescent inverted organic light-emitting devices (IOLEDs) with self or intentionally Ag-doped interlayer modified cathode were demonstrated. The IOLEDs show low driving voltage and high efficiency. For example, the efficiency of inverted bottom-emitting OLED with ITO cathode is comparable with the conventional bottom-emitting OLED with ITO anode. The top-emitting IOLED with Ag cathode shows high current efficiency of 76.4 cd/A which is 2.38 times of that of the conventional bottom-emitting OLED with ITO anode. The results indicate that the electron injection from cathode was observably improved by the Ag-doped interlayer and such interlayer is cathode independent relatively.

  18. Homogenous Boron-doping in Self-sensitized Carbon Nitride for Enhanced Visible-light Photocatalytic Activity.

    PubMed

    Gu, Quan; Liu, Jianni; Gao, Ziwei; Xue, Can

    2016-11-22

    We report a solvothermal approach for the preparation of homogeneously B-doped self-sensitized carbon nitride (B-SSCN) composed of a core of B-doped carbon nitride microspheres and a covalently linked shell of s-triazine oligomers. Compared to the undoped structure, the obtained B-SSCN photocatalyst exhibits an enhanced visible-light activity, excellent stability for photocatalytic hydrogen generation due to a reduced band-gap, enhanced charge-separation efficiency, and better surface reactivity of B-SSCN. This work provides a new strategy to uniformly insert heteroatoms into the polymeric carbon nitride framework for the development of metal-free photocatalysts towards efficient production of solar fuels.

  19. Application of visible-light photocatalysis with nitrogen-doped or unmodified titanium dioxide for control of indoor-level volatile organic compounds.

    PubMed

    Jo, Wan-Kuen; Kim, Jong-Tae

    2009-05-15

    The present study evaluated visible-light photocatalysis, applying an annular reactor coated with unmodified or nitrogen (N)-doped titanium dioxide (TiO(2)), to cleanse gaseous volatile organic compounds (VOCs) at indoor levels. The surface chemistry investigation of N-doped TiO(2) suggested that there was no significant residual of sulfate ions or urea species on the surface of the N-doped TiO(2). Under visible-light irradiation, the photocatalytic technique using N-doped TiO(2) was much superior to that for unmodified TiO(2) for the degradation of VOCs. Moreover, the degradation efficiency by a reactor coated with N-doped TiO(2) was well above 90% for four target compounds (ethyl benzene, o,m,p-xylenes), suggesting that this photocatalytic system can be effectively employed to cleanse these pollutants at indoor air quality (IAQ) levels. The degradation efficiency of all target compounds increased as the stream flow rate (SFR) decreased. For most target compounds, a reactor with a lower hydraulic diameter (HD) exhibited elevated degradation efficiency. The result on humidity effect suggested that the N-doped photocatalyst could be employed effectively to remove four target compounds (ethyl benzene, o,m,p-xylenes) under conditions of less humidified environments, including a typical indoor comfort range (50-60%). Consequently, it is suggested that with appropriate photocatalytic conditions, a visible-light-assisted N-doped photocatalytic system is clearly an important tool for improving IAQ.

  20. Anisotropic softening of magnetic excitations in lightly electron-doped Sr2IrO4

    DOE PAGES

    Liu, X.; Dean, M. P. M.; Meng, Z. Y.; ...

    2016-06-10

    The magnetic excitations in electron doped (Sr1-xLax)2IrO4 with x = 0:03 were measured using resonant inelastic X-ray scattering at the Ir L3-edge. Although much broadened, well defined dispersive magnetic excitations were observed. Comparing with the magnetic dispersion from the undoped compound, the evolution of the magnetic excitations upon doping is highly anisotropic. Along the anti-nodal direction, the dispersion is almost intact. On the other hand, the magnetic excitations along the nodal direction show significant softening. These results establish the presence of strong magnetic correlations in electron doped (Sr1-xLax)2IrO4 with close analogies to the hole doped cuprates, further motivating the searchmore » for high temperature superconductivity in this system.« less

  1. Anisotropic softening of magnetic excitations in lightly electron-doped Sr2IrO4

    SciTech Connect

    Liu, X.; Dean, M. P. M.; Meng, Z. Y.; Upton, M. H.; Qi, T.; Gog, T.; Cao, Y.; Lin, J. Q.; Meyers, D.; Ding, H.; Cao, G.; Hill, J. P.

    2016-06-10

    The magnetic excitations in electron doped (Sr1-xLax)2IrO4 with x = 0:03 were measured using resonant inelastic X-ray scattering at the Ir L3-edge. Although much broadened, well defined dispersive magnetic excitations were observed. Comparing with the magnetic dispersion from the undoped compound, the evolution of the magnetic excitations upon doping is highly anisotropic. Along the anti-nodal direction, the dispersion is almost intact. On the other hand, the magnetic excitations along the nodal direction show significant softening. These results establish the presence of strong magnetic correlations in electron doped (Sr1-xLax)2IrO4 with close analogies to the hole doped cuprates, further motivating the search for high temperature superconductivity in this system.

  2. A comparison study of rhodamine B photodegradation over nitrogen-doped lamellar niobic acid and titanic acid under visible-light irradiation.

    PubMed

    Li, Xiukai; Kikugawa, Naoki; Ye, Jinhua

    2009-01-01

    A solid-state reaction method with urea as a nitrogen precursor was used to prepare nitrogen-doped lamellar niobic and titanic solid acids (i.e., HNb(3)O(8) and H(2)Ti(4)O(9)) with different acidities for visible-light photocatalysis. The photocatalytic activities of the nitrogen-doped solid acids were evaluated for rhodamine B (RhB) degradation and the results were compared with those obtained over the corresponding nitrogen-doped potassium salts. Techniques such as XRD, BET, SEM, X-ray photoelectron spectroscopy, and UV-visible diffuse reflectance spectroscopy were adopted to explore the nature of the materials as well as the characteristics of the doped nitrogen species. It was found that the intercalation of the urea precursor helped to stabilize the layered structures of both lamellar solid acids and enabled easier nitrogen doping. The effects of urea intercalation were more significant for the more acidic HNb(3)O(8) sample than for the less acidic H(2)Ti(4)O(9). Compared with the nitrogen-doped KNb(3)O(8) and K(2)Ti(4)O(9) samples, the nitrogen-doped HNb(3)O(8) and H(2)Ti(4)O(9) solid acids absorb more visible light and exhibit a superior activity for RhB photodegradation under visible-light irradiation. The nitrogen-doped HNb(3)O(8) sample performed the best among all the samples. The results of the current study suggest that the protonic acidity of the lamellar solid-acid sample is a key factor that influences nitrogen doping and the resultant visible-light photocatalysis.

  3. Band alignment and photon extraction studies of Na-doped MgZnO/Ga-doped ZnO heterojunction for light-emitter applications

    SciTech Connect

    Pandey, Sushil Kumar; Awasthi, Vishnu; Sengar, Brajendra Singh; Garg, Vivek; Sharma, Pankaj; Mukherjee, Shaibal; Kumar, Shailendra; Mukherjee, C.

    2015-10-28

    Ultraviolet photoelectron spectroscopy is carried out to measure the energy discontinuity at the interface of p-type Na-doped MgZnO (NMZO)/n-type Ga-doped ZnO (GZO) heterojunction grown by dual ion beam sputtering. The offset values at valence band and conduction band of NMZO/GZO heterojunction are calculated to be 1.93 and −2.36 eV, respectively. The p-type conduction in NMZO film has been confirmed by Hall measurement and band structure. Moreover, the effect of Ar{sup +} ion sputtering on the valence band onset values of NMZO and GZO thin films has been investigated. This asymmetric waveguide structure formed by the lower refractive index of GZO than that of NMZO indicates that easy extraction of photons generated in GZO through the NMZO layer into free space. The asymmetric waveguide structure has potential applications to produce ZnO-based light emitters with high extraction efficiency.

  4. Universality of pseudogap and emergent order in lightly doped Mott insulators

    NASA Astrophysics Data System (ADS)

    Battisti, I.; Bastiaans, K. M.; Fedoseev, V.; de la Torre, A.; Iliopoulos, N.; Tamai, A.; Hunter, E. C.; Perry, R. S.; Zaanen, J.; Baumberger, F.; Allan, M. P.

    2017-01-01

    It is widely believed that high-temperature superconductivity in the cuprates emerges from doped Mott insulators. When extra carriers are inserted into the parent state, the electrons become mobile but the strong correlations from the Mott state are thought to survive--inhomogeneous electronic order, a mysterious pseudogap and, eventually, superconductivity appear. How the insertion of dopant atoms drives this evolution is not known, nor is whether these phenomena are mere distractions specific to hole-doped cuprates or represent genuine physics of doped Mott insulators. Here we visualize the evolution of the electronic states of (Sr1-xLax)2IrO4, which is an effective spin-1/2 Mott insulator like the cuprates, but is chemically radically different. Using spectroscopic-imaging scanning tunnelling microscopy (SI-STM), we find that for a doping concentration of x ~ 5%, an inhomogeneous, phase-separated state emerges, with the nucleation of pseudogap puddles around clusters of dopant atoms. Within these puddles, we observe the same iconic electronic order that is seen in underdoped cuprates. We investigate the genesis of this state and find evidence at low doping for deeply trapped carriers, leading to fully gapped spectra, which abruptly collapse at a threshold of x ~ 4%. Our results clarify the melting of the Mott state, and establish phase separation and electronic order as generic features of doped Mott insulators.

  5. White organic light-emitting diodes based on a combined electromer and monomer emission in doubly-doped polymers

    NASA Astrophysics Data System (ADS)

    Meng, Ling-Chuan; Lou, Zhi-Dong; Yang, Sheng-Yi; Hou, Yan-Bing; Teng, Feng; Liu, Xiao-Jun; Li, Yun-Bai

    2012-08-01

    We report on white organic light-emitting diodes (WOLEDs) based on polyvinylcarbazole (PVK) doped with 1,1-bis((di-4-tolylamino)phenyl)cyclohexane (TAPC) and perylene, and investigate the luminescence mechanism of the devices. The chromaticity of light emission can be tuned by adjusting the concentration of the dopants. White light with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.33, 0.34) is achieved by mixing the yellow electromer emission of TAPC and the blue monomer emission of perylene from the device ITO/PVK: TAPC: perylene (100:9:1 in wt.) (100 nm)/tris-(8-hydroxyquinoline aluminum (Alq3) (10 nm)/Al. The device exhibits a maximal luminance of 3727 cd/m2 and a current efficiency of 2 cd/A.

  6. Visible light photocatalytic degradation of 4-chlorophenol using vanadium and nitrogen co-doped TiO{sub 2}

    SciTech Connect

    Jaiswal, R.; Kothari, D. C.; Patel, N.; Miotello, A.

    2013-02-05

    Vanadium and Nitrogen were codoped in TiO{sub 2} photocatalyst by Sol-gel method to utilize visible light more efficiently for photocatalytic reactions. A noticeable shift of absorption edge to visible light region was obtained for the singly-doped namely V-TiO{sub 2}, N-TiO{sub 2} and codoped V-N-TiO{sub 2} samples in comparison with undoped TiO{sub 2}, with smallest band gap obtained with codoped-TiO{sub 2}. The photocatalytic activities for all TiO{sub 2} photocatalysts were tested by 4-chlorophenol (organic pollutant) degradation under visible light irradiation. It was found that codoped TiO{sub 2} exhibits the best photocatalytic activity, which could be attributed to the synergistic effect produced by V and N dopants.

  7. Visible light photocatalytic degradation of 4-chlorophenol using vanadium and nitrogen co-doped TiO2

    NASA Astrophysics Data System (ADS)

    Jaiswal, R.; Patel, N.; Kothari, D. C.; Miotello, A.

    2013-02-01

    Vanadium and Nitrogen were codoped in TiO2 photocatalyst by Sol-gel method to utilize visible light more efficiently for photocatalytic reactions. A noticeable shift of absorption edge to visible light region was obtained for the singly-doped namely V-TiO2, N-TiO2 and codoped V-N-TiO2 samples in comparison with undoped TiO2, with smallest band gap obtained with codoped-TiO2. The photocatalytic activities for all TiO2 photocatalysts were tested by 4-chlorophenol (organic pollutant) degradation under visible light irradiation. It was found that codoped TiO2 exhibits the best photocatalytic activity, which could be attributed to the synergistic effect produced by V and N dopants.

  8. Pd-doped Bi2MoO6 plasmonic photocatalysts with enhanced visible light photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Meng, Xiangchao; Zhang, Zisheng

    2017-01-01

    Pd-doped Bi2MoO6 was prepared and investigated for the first time. The prepared samples were characterized by their crystal structures, chemical states, atomic compositions, optical properties and morphologies. The photocatalytic activities of prepared samples under visible light irradiation were determined by degradation of phenol, which is widely found in wastewater from many industrial processes and is difficult to destroy. The sample exhibiting the highest removal efficiency with respect to the degradation of phenol contained 2% Pd. The enhancement effect can be interpreted as the integrated effects of a reduction in the rate of electron-hole recombination, surface plasmon resonance, and production of Cl0. This work sheds light on the potential applications of noble metal nanoparticles in visible light-driven photocatalysis.

  9. Mechanisms of lighting enhancement of Al nanoclusters-embedded Al-doped ZnO film in GaN-based light-emitting diodes

    SciTech Connect

    Lee, Hsin-Ying; Chou, Ying-Hung; Lee, Ching-Ting

    2010-01-15

    Aluminum (Al)-doped ZnO (AZO) films with embedded Al nanoclusters were proposed and utilized to enhance the light output power and maximum operation current of GaN-based light-emitting diodes (LEDs). The AZO films were sputtered using ZnO and Al targets in a magnetron cosputtering system. With Al dc power of 7 W and ZnO 100 W ac power, the electron concentration of 4.1x10{sup 20} cm{sup -3}, electron mobility of 16.2 cm{sup 2}/V s, and resistivity of 7.2x10{sup -4} {Omega} cm were obtained for the deposited AZO film annealed at 600 deg. C for 1 min in a N{sub 2} ambient. As verified by a high resolution transmission electron microscopy, the deposited AZO films with embedded Al nanoclusters were clearly observed. A 35% increase in light output power of the GaN-based LEDs with Al nanoclusters-embedded AZO films was realized compared with the conventional LEDs operated at 500 mA. It was verified experimentally that the various characteristics of GaN-based LEDs including the antireflection, light scattering, current spreading, and the light extraction efficiency in light emission could be significantly enhanced with the use of Al nanoclusters-embedded AZO films.

  10. Photocarrier Radiometry Investigation of Light-Induced Degradation of Boron-Doped Czochralski-Grown Silicon Without Surface Passivation

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Li, Bincheng

    2016-04-01

    Light-induced degradation (LID) effects of boron-doped Cz silicon wafers without surface passivation are investigated in details by photocarrier radiometry (PCR). The resistivity of all samples is in the range of 0.006 Ω {\\cdot } {cm} to 38 Ω {\\cdot } {cm}. It is found that light-induced changes in surface state occupation have a great effect on LID under illumination. With the increasing contribution of light-induced changes in surface state occupation, the generation rate of the defect decreases. The light-induced changes in surface state occupation and light-induced degradation dominate the temporal behaviors of the excess carrier density of high- and low-resistivity Si wafers, respectively. Moreover, the temporal behaviors of PCR signals of these samples under laser illumination with different powers, energy of photons, and multiple illuminations were also analyzed to understand the light-induced change of material properties. Based on the nonlinear dependence of PCR signal on the excitation power, a theoretical model taking into account both light-induced changes in surface state occupation and LID processes was proposed to explain those temporal behaviors.

  11. A facile one-step electrochemical strategy of doping iron, nitrogen, and fluorine into titania nanotube arrays with enhanced visible light photoactivity.

    PubMed

    Hua, Zulin; Dai, Zhangyan; Bai, Xue; Ye, Zhengfang; Gu, Haixin; Huang, Xin

    2015-08-15

    Highly ordered iron, nitrogen, and fluorine tri-doped TiO2 (Fe, (N, F)-TiO2) nanotube arrays were successfully synthesized by a facile one-step electrochemical method in an NH4F electrolyte containing Fe ions. The morphology, structure, composition, and photoelectrochemical property of the as-prepared nanotube arrays were characterized by various methods. The photoactivities of the samples were evaluated by the degradation of phenol in an aqueous solution under visible light. Tri-doped TiO2 showed higher photoactivities than undoped TiO2 under visible light. The optimum Fe(3+) doping amount at 0.005M exhibited the highest photoactivity and exceeded that of undoped TiO2 by a factor of 20 times under visible light. The formation of N 2p level near the valence band (VB) contributed to visible light absorption. Doping fluorine and appropriate Fe(3+) ions reduced the photogenerated electrons-holes recombination rate and enhanced visible light photoactivity. The X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results indicated the presence of synergistic effects in Fe, N, and F tri-doped TiO2, which enhanced visible light photoactivity. The Fe, (N, F)-TiO2 photocatalyst exhibited high stability.

  12. TiS2 transformation into S-doped and N-doped TiO2 with visible-light catalytic activity

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Chen; Chien, Tzu-En; Lai, Po-Chih; Chiang, Yu-Hsien; Li, Kun-Lin; Lin, Jong-Liang

    2015-12-01

    S-doped rutile has been prepared for the first time by hydrothermal reaction of TiS2 in hydrochloric acid at a low temperature (180 °C), with the S atoms in three states of Tisbnd Ssbnd Ti, Tisbnd Ssbnd O and SO4. TiS2 in nitric acid can also be transformed into TiO2, but with mixed phases of anatase and rutile, containing nitrogen atoms at interstitial sites in the form of Tisbnd Osbnd N or Tisbnd Nsbnd O. The Ssbnd TiO2 catalyst shows a better visible-light reactivity toward adsorbed methylene blue (MB) photodegradation and hydroxylation of terephthalic acid with respect to the Nsbnd TiO2. The possible reasons leading to the high photoactivity of the Ssbnd TiO2 are discussed in terms of the incorporated sulfur states.

  13. Enhanced Performance of Quantum Dot-Based Light-Emitting Diodes with Gold Nanoparticle-Doped Hole Injection Layer.

    PubMed

    Chen, Fei; Lin, Qingli; Wang, Hongzhe; Wang, Lei; Zhang, Fengjuan; Du, Zuliang; Shen, Huaibin; Li, Lin Song

    2016-12-01

    In this paper, the performance of quantum dot-based light-emitting diodes (QLEDs) comprising ZnCdSe/ZnS core-shell QDs as an emitting layer were enhanced by employing Au-doped poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate ( PSS) hole injection layer (HIL). By varying the concentration and dimension of Au nanoparticle (NP) dopants in PSS, the optimal devices were obtained with ~22-nm-sized Au NP dopant at the concentration with an optical density (OD) of 0.21. Highly bright green QLEDs with a maximum external quantum efficiency (EQE) of 8.2 % and a current efficiency of 29.1 cd/A exhibit 80 % improvement compared with devices without Au NP dopants. The improved performance may be attributed to the significant increase in the hole injection rate as a result of the introduction of Au NPs and the good matching between the resonance frequency of the localized surface plasmon resonance (LSPR) generated by the Au NPs and the emission band of QD layer, as well as the suppressed Auger recombination of QD layer due to the LSPR-induced near-field enhanced radiative recombination rate of excitons. These results are helpful for fabricating high-performance QD-based applications, such as full-color displays and solid-state lighting. 80 % enhancement of efficency of quantum dot-based light-emitting diodes with gold nanoparticle doped hole-injection-layer.

  14. Effective nitrogen doping into TiO2 (N-TiO2) for visible light response photocatalysis.

    PubMed

    Yoshida, Tomoko; Niimi, Satoshi; Yamamoto, Muneaki; Nomoto, Toyokazu; Yagi, Shinya

    2015-06-01

    The thickness-controlled TiO2 thin films are fabricated by the pulsed laser deposition (PLD) method. These samples function as photocatalysts under UV light irradiation and the reaction rate depends on the TiO2 thickness, i.e., with an increase of thickness, it increases to the maximum, followed by decreasing to be constant. Such variation of the reaction rate is fundamentally explained by the competitive production and annihilation processes of photogenerated electrons and holes in TiO2 films, and the optimum TiO2 thickness is estimated to be ca. 10nm. We also tried to dope nitrogen into the effective depth region (ca. 10nm) of TiO2 by an ion implantation technique. The nitrogen doped TiO2 enhanced photocatalytic activity under visible-light irradiation. XANES and XPS analyses indicated two types of chemical state of nitrogen, one photo-catalytically active N substituting the O sites and the other inactive NOx (1⩽x⩽2) species. In the valence band XPS spectrum of the high active sample, the additional electronic states were observed just above the valence band edge of a TiO2. The electronic state would be originated from the substituting nitrogen and be responsible for the band gap narrowing, i.e., visible light response of TiO2 photocatalysts. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Fabrication and enhanced visible light photocatalytic activity of fluorine doped TiO2 by loaded with Ag.

    PubMed

    Lin, Xiaoxia; Rong, Fei; Ji, Xiang; Fu, Degang; Yuan, Chunwei

    2011-11-01

    F-doped TiO2 loaded with Ag (Ag/F-TiO2) was prepared by sol-gel process combined with photoreduction method. The physical and chemical properties of the prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). XPS analysis indicated Ag species existed as Ag0 in the structure of Ag/F-TiO2 samples. UV-Vis diffuse reflectance spectra showed that the light absorption of Ag/F-TiO2 in the visible region had a significant enhancement compared with the F-doped TiO2 (F-TiO2). PL analysis indicated that the electron-hole recombination rate had been effectively inhibited when Ag loaded on the surface of F-TiO2. The photocatalytic activities of the samples were evaluated for the degradation of X-3B (Reactive Brilliant Red dye, C.I. reactive red 2) under visible light (lambda > 420 nm) irradiation. Compared with F-TiO2, the sample of 0.50 Ag/F-TiO2 showed the highest photocatalytic activity. The interaction between F species and metallic Ag was responsible for improving the visible light photocatalytic activity.

  16. Low-temperature solvothermal synthesis of visible-light-responsive S-doped TiO2 nanocrystal

    NASA Astrophysics Data System (ADS)

    Yang, Guidong; Yan, Zifeng; Xiao, Tiancun

    2012-02-01

    In this work, a low-temperature solvothermal method has been developed to synthesize visible-light-responsive S-doped TiO2 nanocrystal photocatalyst, using thiourea as the sulfur source to enhance sulfur incorporation into TiO2 lattice. The effects of different S:Ti molar ratio on the crystal structure, chemical composition, surface property and catalytic performance have been studied. X-ray photoelectron spectroscopy (XPS) analysis and Fourier transform infrared (FT-IR) spectra displayed that the TiO2 was modified by the S element incorporated into the TiO2 network to form Tisbnd Osbnd S bond, which therefore led to the formation of intermediate energy level just above the O 2p valance band, and caused the absorption edge of TiO2 to shift into the visible light region up to 500 nm. Characterization results show that the pure nanocrystal anatase structure, with both the degree of S doping and oxygen vacancies makes contribution to the exceptional photocatalytic activity of TONS in visible-light degradation of Methylene Blue (MB) and phenol molecules.

  17. Solvothermal synthesis of carbon coated N-doped TiO2 nanostructures with enhanced visible light catalytic activity

    NASA Astrophysics Data System (ADS)

    Yan, Xue-Min; Kang, Jialing; Gao, Lin; Xiong, Lin; Mei, Ping

    2013-01-01

    Visible light-active carbon coated N-doped TiO2 nanostructures(CTS-TiO2) were prepared by a facile one-step solvothermal method with chitosan as carbon and nitrogen resource at 180 °C. The as-prepared samples were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. The CTS-TiO2 nanocomposites possess anatase phase of nanocrystalline structure with average particle size of about 5-7 nm. A wormhole mesostructure can be observed in the CTS-TiO2 nanocomposites due to the constituent agglomerated of nanoparticles. It has been evidenced that the nitrogen was doped into the anatase titania lattice and the carbon species were modified on the surface of TiO2. The photocatalytic activities of the as-prepared photocatalysts were measured by the degradation of methylene blue (MB) under visible light irradiation at λ ≥ 400 nm. The results show that CTS-TiO2 nanostructures display a higher visible light photocatalytic activity than pure TiO2, commercial P25 and C-coated TiO2 (C-TiO2) photocatalysts. The higher photocatalytic activity could be attributed to the band-gap narrowed by N-doping and the accelerated separation of the photo-generated electrons and holes by carbon modification.

  18. Synthesis and characterization of copper-doped zinc sulfide nanomaterials for the application of energy efficient electroluminescent lighting

    NASA Astrophysics Data System (ADS)

    Corrado, Carley

    Doped nanocrystals (NCs) compose an important subset of nanomaterials in which a small percentage of dopant ion is introduced into host semiconductor nanocrystals with the affect of altering their optical properties. Their tunable, intense, and stable emission make them ideal candidates for a number of opto-electronic applications, including use as phosphors for solid-state lighting applications. ZnS doped with Cu (ZnS:Cu) is a commonly used bulk phosphor material and a promising candidate for use as a nanophospor material, though the energy states involved in the electronic transitions leading to luminescence are not well understood. To shed light on this topic, ZnS:Cu nanocrystals were synthesized and their optical properties were correlated with their structure using UV-Vis and photoluminescence (PL) spectroscopy, TEM, EXAFS, XRD, and ICP. The dependence of the optical and structural properties on dopant concentration, shell growth, co-doping, and solvent were explored. Through EXAFS study about the local structure of the Cu-dopant, it was found that Cu was located at or near the surface of the nanocrystals. A ZnS shell was grown around the ZnS:Cu nanocrystals resulting in increased dopant-related PL emission due to encapsulation of the dopant into the core of the nanocrystals. ZnS:Cu nanocrystals were also synthesized in an organic solvent to enable fabrication of high quality films for electroluminescent lighting applications. Addition of Br was added as a co-activator with the effect of greatly enhanced Cu-dopant PL emission. Characterization of the local structure of the Br-dopant using EXAFS confirmed substitutional incorporation of the Br into the core of the ZnS nanocrystals. Methods were developed to enhance dopant-related PL emission.

  19. Characterization and photocatalytic performance evaluation of various metal ion-doped microstructured TiO2 under UV and visible light.

    PubMed

    Sahoo, Chittaranjan; Gupta, Ashok K

    2015-01-01

    Commercially available microcrystalline TiO2 was doped with silver, ferrous and ferric ion (1.0 mol %) using silver nitrate, ferrous sulfate and ferric nitrate solutions following the liquid impregnation technology. The catalysts prepared were characterised by FESEM, XRD, FTIR, DRS, particle size and micropore analysis. The photocatalytic activity of the prepared catalysts was tested on the degradation of two model dyes, methylene blue (3,7-bis (Dimethylamino)-phenothiazin-5-ium chloride, a cationic thiazine dye) and methyl blue (disodium;4-[4-[[4-(4-sulfonatoanilino)phenyl]-[4-(4-sulfonatophenyl)azaniumylidenecyclohexa-2,5-dien-1-ylidene]methyl]anilino]benzene sulfonate, an anionic triphenyl methane dye) under irradiation by UV and visible light in a batch reactor. The efficiency of the photocatalysts under UV and visible light was compared to ascertain the light range for effective utilization. The catalysts were found to have the anatase crystalline structure and their particle size is in a range of 140-250 nm. In the case of Fe(2+) doped TiO2 and Fe(3+) doped TiO2, there was a greater shift in the optical absorption towards the visible range. Under UV light, Ag(+) doped TiO2 was the most efficient catalyst and the corresponding decolorization was more than 99% for both the dyes. Under visible light, Fe(3+) doped TiO2 was the most efficient photocatalyst with more than 96% and 90% decolorization for methylene blue and methyl blue, respectively. The kinetics of the reaction under both UV and visible light was investigated using the Langmuir-Hinshelwood pseudo-first-order kinetic model. Kinetic measurements confirmed that, Ag(+) doped TiO2 was most efficient in the UV range, while Fe(3+) doped TiO2 was most efficient in the visible range.

  20. Role of Li+ on white light emission from Sm3+ and Tb3+ co-doped Y2O3 nano-phosphor

    NASA Astrophysics Data System (ADS)

    Yadav, R. S.; Yadav, R. V.; Bahadur, A.; Yadav, T. P.; Rai, S. B.

    2016-03-01

    This paper reports on white light emission from Sm3+ and Tb3+ co-doped Y2O3 nano-phosphor, synthesized through the solution combustion method. The XRD and TEM measurements of the nano-phosphors reveal a crystalline nature and spherical particle distribution. The Sm3+-doped nano-phosphor gives off an orange-red emission whereas the Tb3+-doped nano-phosphor gives off blue and green emissions individually on excitation with 380 nm radiation. When the Sm3+and Tb3+ ions are doped together, the co-doped nano-phosphor emits white light with the CIE coordinates 0.33 and 0.37, due to the combined emissions of these two ions on excitation with 380 nm radiation. The color of the emitted light is tunable with the concentration of Sm3+ ions, and it emits white light at the 2.0 mol% concentration of Sm3+ and 1.0 mol% concentration of Tb3+ ions. The nano-phosphor sample annealed at a higher temperature results in a greater emission intensity. The presence of Li+ ions in the co-doped sample enhances the emission intensity of white light up to three times. The enhancement in the emission intensity is discussed in terms of a reduction in the optical quenching centers and an increase in the crystallite size. The Sm3+ and Tb3+ co-doped Y2O3 nano-phosphor in the presence of Li+ is a suitable candidate for white light in a solid state display.

  1. Temperature dependent x-ray diffraction study of lightly doped Na{sub x}WO{sub 3}

    SciTech Connect

    Paul, Sanhita; Mukherjee, G. D.; Ghosh, Anirudha; Raj, Satyabrata; Oishi, S.

    2011-03-21

    Temperature dependent x-ray diffraction studies have been carried out on nonstoichiometric lightly doped sodium tungsten bronze (Na{sub x}WO{sub 3} for x=0.025). The investigation reveals a structural modification around 230 K. Although the high and low temperature phases are monoclinic but at low temperature the corner sharing WO{sub 6} octahedra get significantly distorted due to displacement of tungsten and oxygen atoms from its mean position. This structural modification induces polaron formation in Na{sub 0.025}WO{sub 3} below 230 K.

  2. Dependence of efficiencies in GaN-based vertical blue light-emitting diodes on the thickness and doping concentration of the n-GaN layer.

    PubMed

    Ryu, Han-Youl; Jeon, Ki-Seong; Kang, Min-Goo; Choi, Yunho; Lee, Jeong-Soo

    2013-01-14

    We investigate the dependence of various efficiencies in GaN-based vertical blue light-emitting diode (LED) structures on the thickness and doping concentration of the n-GaN layer by using numerical simulations. The electrical efficiency (EE) and the internal quantum efficiency (IQE) are found to increase as the thickness or doping concentration increases due to the improvement of current spreading. On the contrary, the light extraction efficiency (LEE) decreases with increasing doping concentration or n-GaN thickness by the free-carrier absorption. By combining the results of EE, IQE, and LEE, wall-plug efficiency (WPE) of the vertical LED is calculated, and the optimum thickness and doping concentration of the n-GaN layer is found for obtaining the maximum WPE.

  3. Intense white light emission in Tm3+/Er3+/Yb3+ co-doped Y2O3-ZnO nano-composite

    NASA Astrophysics Data System (ADS)

    Yadav, R. S.; Verma, R. K.; Rai, S. B.

    2013-07-01

    The Tm3+/Er3+/Yb3+ co-doped Y2O3-ZnO nano-composite is synthesized using the solution combustion technique. The structural morphology is monitored using x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The Yb3+/Tm3+ co-doped nano-phosphor emits intense blue as well as weak red emissions, while Yb3+/Er3+ co-doped nano-phosphor emits strong green along with red emissions on excitation with 976 nm laser. Joining these together (i.e. Tm3+/Er3+/Yb3+ co-doped phosphor) give very strong white light, which is further verified by CIE coordinates (0.32, 0.36). The addition of ZnO with Y2O3 phosphor gives further enhancement in the intensity of white light. The possible reason for this enhancement is the removal of optical quenching sites.

  4. Fabrication, photoluminescence, and potential application in white light emitting diode of Dy3+-Tm3+ doped transparent glass ceramics containing GdSr2F7 nanocrystals

    NASA Astrophysics Data System (ADS)

    Wang, X. F.; Yan, X. H.; Bu, Y. Y.; Zhen, J.; Xuan, Y.

    2013-08-01

    Dy3+-Tm3+ doped transparent glass ceramics containing GdSr2F7 nanocrystals were fabricated successfully by a melt-quenching method and subsequent heating. X-ray diffraction and transmission electron microscopy analyses show that tetragonal GdSr2F7 nanocrystals are homogeneously precipitated among the borosilicate glass matrix. If excited with 354 nm UV light, the photoluminescence spectrum of Dy3+ single-doped transparent glass ceramics shows white-light emission. With doping of Tm3+, the overall emission color of Tm3+-Dy3+ co-doped transparent glass ceramics can be tuned from white to blue through energy transfer between Dy3+ and Tm3+. CIE chromaticity and color temperature measurements show that the resulting TGCS may be a candidate as a white LED material pumped by a UV InGaN chip.

  5. Temperature dependent electrical characteristics of Pt Schottky barriers fabricated on lightly and highly doped n-type 4H-SiC

    NASA Astrophysics Data System (ADS)

    Huang, Lingqin; Wang, Dejun

    2015-11-01

    The temperature dependent electronic characteristics of Pt Schottky barriers fabricated on lightly and relatively highly doped n-type 4H-SiC (1 × 1016 and 1 × 1018 cm-3) are comparatively investigated. It is found that the abnormal temperature dependence of barrier height and ideality factor estimated from the thermionic emission (TE) model for both lightly and highly doped samples could be successfully explained in terms of Gaussian distribution of inhomogeneous barrier heights. However, the estimated mean barrier height according to Gaussian distribution for the highly doped sample is much lower than the actual mean value from the capacitance-voltage (C-V) measurements. Interestingly, the values of barrier height from the thermionic field emission (TFE) model are found to be close to those from the C-V measurements, indicating that the TFE model is more appropriate to explain the electrical transport for the highly doped sample.

  6. Effect of Vanadium(IV)-Doping on the Visible Light-Induced Catalytic Activity of Titanium Dioxide Catalysts for Methylene Blue Degradation

    PubMed Central

    Lin, Wen-Churng; Lin, Yo-Jane

    2012-01-01

    Abstract Vanadium(IV)-doped titanium dioxide (TiO2) photocatalyst powders were prepared by the sol–gel method and characterized by Brunauer–Emmett–Teller–specific surface area, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet-visible spectroscopy. V-doping in the TiO2 increases the crystal grain size, which decreases the specific surface areas of powders. This V-doping changes the band gap of TiO2, leading to extend the absorption to visible light regions (400–800 nm). Photocatalytic degradation of methylene blue (MB) in water was investigated as a function of the vanadium content in TiO2 and was found to follow pseudo first-order rate kinetics. Appropriate content of V-doping is an effective means to improve the photocatalytic activity of TiO2 for MB degradation under visible light irradiation. PMID:22693413

  7. A CMOS time-of-flight range image sensor using draining only modulation structure

    NASA Astrophysics Data System (ADS)

    Han, Sangman; Yasutomi, Keita; Kagawa, Keiichiro; Kawahito, Shoji

    2014-03-01

    This paper presents new structure and method of charge modulation for CMOS ToF range image sensors using pinned photodiodes. Proposed pixel structure, the draining only modulator (DOM), allows us to achieve high-speed charge transfer by generating lateral electric field from the pinned photo-diode (PPD) to the pinned storage-diode (PSD). Generated electrons by PPD are transferred to the PSD or drained off through the charge draining gate (TXD). This structure realizes trapping-less charge transfer from the PPD to PSD. To accelerate the speed of charge transfer, the generation of high lateral electric field is necessary. To generate the electric field, the width of the PPD is changed along the direction of the charge transfer. The PPD is formed by the p+ and n layer on the p-substrate. The PSD is created by doping another n type layer for higher impurity concentration than that of the n layer in the PPD. This creates the potential difference between the PPD and PSD. Another p layer underneath the n-layer of the PSD is created for preventing the injection of unwanted carrier from the substrate to the PSD. The range is calculated with signals in the three consecutive sub-frames; one for delay sensitive charge by setting the light pulse timing at the edge of TXD pulse, another for delay independent charge by setting the light pulse timing during the charge transfer, and the other for ambient light charge by setting the light pulse timing during the charge draining. To increase the photo sensitivity while realizing high-speed charge transfer, the pixel consists of 16 sub-pixels and a source follower amplifier. The outputs of 16 sub-pixels are connected to a charge sensing node which has MOS capacitor for increasing well capacity. The pixel array has 313(Row) x 240(Column) pixels and the pixel pitch is 22.4μm. A ToF range imager prototype using the DOM pixels is designed and implemented with 0.11um CMOS image sensor process. The accumulated signal intensity in the PSD

  8. Ultraviolet-light-driven doping modulation in chemical vapor deposition grown graphene.

    PubMed

    Iqbal, M Z; Iqbal, M W; Khan, M F; Eom, Jonghwa

    2015-08-28

    The tuning of charge carrier density of graphene is an essential factor to achieve the integration of high-efficiency electronic and optoelectronic devices. We demonstrate the reversible doping in graphene using deep ultraviolet (UV) irradiation and treatment with O2 and N2 gases. The Dirac point shift towards a positive gate voltage of chemical vapor deposition grown graphene field-effect transistors confirms the p-type doping, which is observed under UV irradiation and treatment with O2 gas, while it restores its pristine state after treatment with N2 gas under UV irradiation. The emergence of an additional peak in the X-ray photoelectron spectra during UV irradiation and treatment with O2 gas represents the oxidation of graphene, and the elimination of this peak during UV irradiation and treatment with N2 gas reveals the restoration of graphene in its pristine state. The shift in the G and 2D bands in Raman spectra towards higher and then lower wavenumber also suggests p-type doping and then reversible doping in graphene. The controlled doping and its reversibility in large area grown graphene offer a new vision for electronic applications.

  9. Synthesis and characterization of white light-emitting Dy3+-doped Gd2O3 nanophosphors

    NASA Astrophysics Data System (ADS)

    Nambram, S.; Singh, S. D.; Meetei, S. D.

    2016-03-01

    A series of Gd2O3 nanophosphors doped with different concentration of Dy3+ has been synthesized by chemical precipitation method. X-ray diffraction study of the undoped and doped samples suggests that Dy3+ atoms remain in the crystallite cubic lattice of the host. The particle sizes are in the range of 14-19 nm. Energy-dispersive analysis of X-ray spectroscopy study and Fourier transform infrared spectroscopy studies are also performed to analyze the elements present in the samples. Photoluminescence emission peak of Dy3+ in doped samples are observed at 487, 575 and 672 nm corresponding to the 4F9/2-6H15/2, 4F9/2-6H13/2 and 4F9/2-6H11/2 transition, respectively. Effective energy transfer from Gd3+ to Dy3+ is observed, yielding efficient emission under UV excitation. The maximum emission intensity is found at 1.5 at.% Dy3+-doped Gd2O3 sample. The enhancement in the emission intensity with the increase in Dy3+ is due to the increase in energy transfer from Gd3+ of host to Dy3+ ions. The CIE ( Commission Internationale de l'é clairage) coordinates of the doped samples are found to be very close to that of standard white color (0.33, 0.33).

  10. Enhanced Photocatalytic Activity for H2 Evolution under Irradiation of UV–Vis Light by Au-Modified Nitrogen-Doped TiO2

    PubMed Central

    Zhao, Weirong; Ai, Zhuyu; Dai, Jiusong; Zhang, Meng

    2014-01-01

    Background Purpose Photocatalytic water splitting for hydrogen evolution is a potential way to solve many energy and environmental issues. Developing visible-light-active photocatalysts to efficiently utilize sunlight and finding proper ways to improve photocatalytic activity for H2 evolution have always been hot topics for research. This study attempts to expand the use of sunlight and to enhance the photocatalytic activity of TiO2 by N doping and Au loading. Methods Au/N-doped TiO2 photocatalysts were synthesized and successfully used for photocatalytic water splitting for H2 evolution under irradiation of UV and UV–vis light, respectively. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and photoelectrochemical characterizations. Results DRS displayed an extension of light absorption into the visible region by doping of N and depositing with Au, respectively. PL analysis indicated electron-hole recombination due to N doping and an efficient inhibition of electron-hole recombination due to the loaded Au particles. Under the irradiation of UV light, the photocatalytic hydrogen production rate of the as-synthesized samples followed the order Au/TiO2 > Au/N-doped TiO2 > TiO2 > N-doped TiO2. While under irradiation of UV–vis light, the N-TiO2 and Au/N-TiO2 samples show higher H2 evolution than their corresponding nitrogen-free samples (TiO2 and Au/TiO2). This inconsistent result could be attributed to the doping of N and the surface plasmonic resonance (SPR) effect of Au particles extending the visible light absorption. The photoelectrochemical characterizations further indicated the enhancement of the visible light response of Au/N-doped TiO2. Conclusion Comparative studies have shown that a combination of nitrogen doping and Au loading enhanced the visible light response of TiO2 and

  11. Enhanced photocatalytic activity for H2 evolution under irradiation of UV-vis light by Au-modified nitrogen-doped TiO2.

    PubMed

    Zhao, Weirong; Ai, Zhuyu; Dai, Jiusong; Zhang, Meng

    2014-01-01

    Photocatalytic water splitting for hydrogen evolution is a potential way to solve many energy and environmental issues. Developing visible-light-active photocatalysts to efficiently utilize sunlight and finding proper ways to improve photocatalytic activity for H2 evolution have always been hot topics for research. This study attempts to expand the use of sunlight and to enhance the photocatalytic activity of TiO2 by N doping and Au loading. Au/N-doped TiO2 photocatalysts were synthesized and successfully used for photocatalytic water splitting for H2 evolution under irradiation of UV and UV-vis light, respectively. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and photoelectrochemical characterizations. DRS displayed an extension of light absorption into the visible region by doping of N and depositing with Au, respectively. PL analysis indicated electron-hole recombination due to N doping and an efficient inhibition of electron-hole recombination due to the loaded Au particles. Under the irradiation of UV light, the photocatalytic hydrogen production rate of the as-synthesized samples followed the order Au/TiO2 > Au/N-doped TiO2 > TiO2 > N-doped TiO2. While under irradiation of UV-vis light, the N-TiO2 and Au/N-TiO2 samples show higher H2 evolution than their corresponding nitrogen-free samples (TiO2 and Au/TiO2). This inconsistent result could be attributed to the doping of N and the surface plasmonic resonance (SPR) effect of Au particles extending the visible light absorption. The photoelectrochemical characterizations further indicated the enhancement of the visible light response of Au/N-doped TiO2. Comparative studies have shown that a combination of nitrogen doping and Au loading enhanced the visible light response of TiO2 and increased the utilization of solar energy, greatly

  12. Visible-Light-Induced Activity Control of Peroxidase Bound to Fe-Doped Titanate Nanosheets with Nanometric Lateral Dimensions.

    PubMed

    Kamada, Kai; Ito, Daiki; Soh, Nobuaki

    2015-10-21

    Catalytic performance of horseradish peroxidase (HRP) electrostatically adsorbed on nanometric and semiconducting Fe-doped titanate (FT) nanosheets was successfully manipulated by visible light illumination. A colloidal solution of FT with a narrow band gap corresponding to a visible light region was fabricated through a hydrolysis reaction of metals sources. HRP could be easily bound to the FT at pH = 4 through an electrostatic interaction between them, and the formed HRP-FT was utilized for the visible-light-driven enzymatic reaction. Under exposure to visible light with enough energy for band gap excitation of the FT, catalytic activity of HRP-FT was dramatically enhanced as compared with free (unbound) HRP and was simply adjusted by light intensity. In addition, wavelength dependence of an enzymatic reaction rate was analogous to an optical absorption spectrum of the FT. These results substantiated an expected reaction mechanism in which the photoenzymatic reaction was initiated by band gap excitation of FT followed by transferring holes generated in the valence band of irradiated FT to HRP. The excited HRP oxidized substrates (amplex ultrared: AUR) accompanied by two-electron reduction to regenerate the resting state. In addition, the catalytic activity was clearly switched by turning on and off the light source.

  13. Lithium hydride doped intermediate connector for high-efficiency and long-term stable tandem organic light-emitting diodes.

    PubMed

    Ding, Lei; Tang, Xun; Xu, Mei-Feng; Shi, Xiao-Bo; Wang, Zhao-Kui; Liao, Liang-Sheng

    2014-10-22

    Lithium hydride (LiH) is employed as a novel n-dopant in the intermediate connector for tandem organic light-emitting diodes (OLEDs) because of its easy coevaporation with other electron transporting materials. The tandem OLEDs with two and three electroluminescent (EL) units connected by a combination of LiH doped 8-hydroxyquinoline aluminum (Alq3) and 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) demonstrate approximately 2-fold and 3-fold enhancement in current efficiency, respectively. In addition, no extra voltage drop across the intermediate connector is observed. Particularly, the lifetime (T75%) in the tandem OLED with two and three EL units is substantially improved by 3.8 times and 7.4 times, respectively. The doping effect of LiH into Alq3, the charge injection, and transport characteristics of LiH-doped Alq3 are further investigated by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS).

  14. Syntheses, structures, tunable emission and white light emitting Eu3+ and Tb3+ doped lanthanide metal-organic framework materials.

    PubMed

    Ma, Ming-Li; Ji, Can; Zang, Shuang-Quan

    2013-08-07

    A series of novel lanthanide metal-organic frameworks, namely, {[Ln2(L)2]·(H2O)3·(Me2NH2)2}n (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Ho (9), Er (10)), have been synthesized with hydro(solvo)thermal conditions based on a flexible multicarboxylic acid (H4L = 5-(3,5-dicarboxybenzyloxy)isophthalic acid). Single crystal X-ray diffraction reveals that all of them are isomorphous and possess a (6,6) topological net with a Schläfli symbol of {4(8)·6(7)}. Considering the blue-emission of compound 1 and the intense emission of the Eu and Tb compounds, we successfully construct isostructural Eu(3+) doped Tb compounds whose color can be tuned easily by adjusting the different concentration of the doped ions, and we also obtained white light emitting materials through the doping of Eu and Tb ions in the La compounds.

  15. Structural, thermal, optical properties and simulation of white light of titanium-tungstate-tellurite glasses doped with dysprosium

    SciTech Connect

    Jyothi, L.; Upender, G.; Kuladeep, R.; Rao, D. Narayana

    2014-02-01

    Graphical abstract: CIE coordinate diagram of different concentrations of the Dy{sup 3+}-doped TTWD glasses with coordinates in the white light region. - Highlights: • Radiative lifetime of {sup 4}F{sub 9/2} level of Dy{sup 3+} ions is longer in the tellurite glass. • Quantum efficiency is found to be high. • These glasses are suitable materials for generating white light. - Abstract: Structural, thermal, optical properties and simulation of white light of Dy{sup 3+}-doped tellurite glasses of composition TTWD: (75 − x)TeO{sub 2} − 10TiO{sub 2} − 15WO{sub 3} − xDy{sub 2}O{sub 3} (x = 0, 0.1, 0.5, 1.0 and 2.0 mol%) were investigated. Raman spectra revealed that the glass contains TeO{sub 4}, TeO{sub 3}, WO{sub 4} and WO{sub 6} units. Differential scanning calorimetry (DSC) measurements were carried out to measure the glass transition temperature of all the glasses. From the optical absorption spectra, luminescence spectra and using the Judd–Ofelt (JO) analysis, we estimated the radiative transition probabilities, emission cross-sections, branching ratios and radiative lifetimes. The decay curves at lower concentrations are exponential while they show a non-exponential behavior at higher concentrations (≥0.5 mol%) due to energy transfer processes. The effective lifetime for the {sup 4}F{sub 9/2} level decreases with increase in Dy{sub 2}O{sub 3} concentration for the glasses under investigation. The non-exponential decay curves could fit well to the Inokuti–Hirayama (IH) model with S = 6, indicating that the nature of interaction responsible for energy transfer is of dipole–dipole type. Simulation of white light is examined with varying concentration and the results indicate that these glasses are suitable for white light emitting diode applications.

  16. Deposition of Visible Light-Active C-Doped Titania Films via Magnetron Sputtering Using CO₂ as a Source of Carbon.

    PubMed

    Klaysri, Rachan; Ratova, Marina; Praserthdam, Piyasan; Kelly, Peter J

    2017-05-16

    Doping of titanium dioxide with p-block elements is typically described as an efficient pathway for the enhancement of photocatalytic activity. However, the properties of the doped titania films depend greatly on the production method, source of doping, type of substrate, etc. The present work describes the use of pulsed direct current (pDC) magnetron sputtering for the deposition of carbon-doped titania coatings, using CO₂ as the source of carbon; ratios of O₂/CO₂ were varied through variations of CO₂ flow rates and oxygen flow control setpoints. Additionally, undoped Titanium dioxide (TiO₂) coatings were prepared under identical deposition conditions for comparison purposes. Coatings were post-deposition annealed at 873 K and analysed with scanning electron microscopy (SEM), X-ray diffreaction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The photocatalytic properties of the thin films were evaluated under ultraviolet (UV) and visible light irradiation using methylene blue and stearic acid decomposition tests. Photoinduced hydrophilicity was assessed through measurements of the water contact angle under UV and visible light irradiation. It was found that, though C-doping resulted in improved dye degradation compared to undoped TiO₂, the UV-induced photoactivity of Carbon-doped (C-doped) photocatalysts was lower for both model pollutants used.

  17. Deposition of Visible Light-Active C-Doped Titania Films via Magnetron Sputtering Using CO2 as a Source of Carbon

    PubMed Central

    Klaysri, Rachan; Ratova, Marina; Praserthdam, Piyasan; Kelly, Peter J.

    2017-01-01

    Doping of titanium dioxide with p-block elements is typically described as an efficient pathway for the enhancement of photocatalytic activity. However, the properties of the doped titania films depend greatly on the production method, source of doping, type of substrate, etc. The present work describes the use of pulsed direct current (pDC) magnetron sputtering for the deposition of carbon-doped titania coatings, using CO2 as the source of carbon; ratios of O2/CO2 were varied through variations of CO2 flow rates and oxygen flow control setpoints. Additionally, undoped Titanium dioxide (TiO2) coatings were prepared under identical deposition conditions for comparison purposes. Coatings were post-deposition annealed at 873 K and analysed with scanning electron microscopy (SEM), X-ray diffreaction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The photocatalytic properties of the thin films were evaluated under ultraviolet (UV) and visible light irradiation using methylene blue and stearic acid decomposition tests. Photoinduced hydrophilicity was assessed through measurements of the water contact angle under UV and visible light irradiation. It was found that, though C-doping resulted in improved dye degradation compared to undoped TiO2, the UV-induced photoactivity of Carbon-doped (C-doped) photocatalysts was lower for both model pollutants used. PMID:28509883

  18. Studies on visible light photocatalytic and antibacterial activities of nanostructured cobalt doped ZnO thin films prepared by sol-gel spin coating method

    NASA Astrophysics Data System (ADS)

    Poongodi, G.; Anandan, P.; Kumar, R. Mohan; Jayavel, R.

    2015-09-01

    Nanostructured cobalt doped ZnO thin films were deposited on glass substrate by sol-gel spin coating technique and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and UV-Vis spectroscopy. The XRD results showed that the thin films were well crystalline with hexagonal wurtzite structure. The results of EDAX and XPS revealed that Co was doped into ZnO structure. FESEM images revealed that the films possess granular morphology without any crack and confirm that Co doping decreases the grain size. UV-Vis transmission spectra show that the substitution of Co in ZnO leads to band gap narrowing. The Co doped ZnO films were found to exhibit improved photocatalytic activity for the degradation of methylene blue dye under visible light in comparison with the undoped ZnO film. The decrease in grain size and extending light absorption towards the visible region by Co doping in ZnO film contribute equally to the improved photocatalytic activity. The bactericidal efficiency of Co doped ZnO films were investigated against a Gram negative (Escherichia coli) and a Gram positive (Staphylococcus aureus) bacteria. The optical density (OD) measurement showed better bactericidal activity at higher level of Co doping in ZnO.

  19. Studies on visible light photocatalytic and antibacterial activities of nanostructured cobalt doped ZnO thin films prepared by sol-gel spin coating method.

    PubMed

    Poongodi, G; Anandan, P; Kumar, R Mohan; Jayavel, R

    2015-09-05

    Nanostructured cobalt doped ZnO thin films were deposited on glass substrate by sol-gel spin coating technique and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and UV-Vis spectroscopy. The XRD results showed that the thin films were well crystalline with hexagonal wurtzite structure. The results of EDAX and XPS revealed that Co was doped into ZnO structure. FESEM images revealed that the films possess granular morphology without any crack and confirm that Co doping decreases the grain size. UV-Vis transmission spectra show that the substitution of Co in ZnO leads to band gap narrowing. The Co doped ZnO films were found to exhibit improved photocatalytic activity for the degradation of methylene blue dye under visible light in comparison with the undoped ZnO film. The decrease in grain size and extending light absorption towards the visible region by Co doping in ZnO film contribute equally to the improved photocatalytic activity. The bactericidal efficiency of Co doped ZnO films were investigated against a Gram negative (Escherichia coli) and a Gram positive (Staphylococcus aureus) bacteria. The optical density (OD) measurement showed better bactericidal activity at higher level of Co doping in ZnO.

  20. M (Tm3+, Tb3+, Ho3+, Dy3+, Mn2+)-doped transparent fluorophosphate glasses for white light-emitting-diodes

    NASA Astrophysics Data System (ADS)

    Ming, Chengguo; Song, Feng; Qin, Yueting; Ren, Xiaobin; An, Liqun

    2014-06-01

    M-doped (M=Tm3+, Tb3+, Ho3+, Dy3+, Mn2+) transparent fluorophosphate glasses were prepared by a high temperature melting method. Excitation and emission spectra of the samples were investigated. Under near-ultraviolet excitation, the emission colors of the Tm3+-and Mn2+-doped samples are blue and red, respectively; the emission colors of the Tb3+-, Ho3+-, and Dy3+-doped samples are green; and the emission color of Tb3+/ Mn2+/Tm3+ tridoped fluorophosphate glass is white to the naked eye. Our research will be helpful in developing luminescent materials for white light-emitting-diodes.

  1. Green light emitting Zn doped β-Ga2O3 nanophosphor

    NASA Astrophysics Data System (ADS)

    Vasanthi, V.; Kottaisamy, M.; Ramakrishnan, V.

    2017-05-01

    The nanoparticles of Zn doped β-Ga2O3 were synthesized by sol-gel combustion method and their structural and optical properties were investigated. The formation of ZnGa2O4-β-Ga2O3 heterostructure by the doping of Zn ions was not affected the absorption and emission band centers, but the replacement of Ga3+ ions by the small amount of Zn2+ reduced the band gap of β-Ga2O3. The defects (O and Ga vacancies) created in the β-Ga2O3 nanoparticles by the doping of Zn2+ ions, which is having lesser oxidation state than that of Ga3+ ions, enhanced the intensity of green emission.

  2. Doping effect on photoabsorption and charge-separation dynamics in light-harvesting organic molecule

    NASA Astrophysics Data System (ADS)

    Ohmura, Satoshi; Tsuruta, Kenji; Shimojo, Fuyuki; Nakano, Aiichiro

    2016-01-01

    Using ab-initio theoretical methods, we demonstrate possible enhancement of photo-conversion efficiency of an organic solar cell via intentional doping in molecular graphene-fullerene heterojunction [the hexabenzocoronene (HBC)-triethylene glycol (TEG)-C60 molecule]. Photoabsorption analysis indicates oxygen substitution into HBC leads to an extension of the spectra up to an infrared regime. A quantum-mechanical molecular dynamics simulation incorporating nonadiabatic electronic transitions reveals that a dissociated charge state (D+ and A-) in the O-doped system is more stable than the pristine case due to the presence of an effective barrier by the TEG HOMO/LUMO level. We also find that oxygen doping in HBC enhances the intermolecular carrier mobility after charge separation. On the other hand, the pristine molecule undergoes rapid recombination between donor and acceptor charges at the interface. These analyses suggest that the graphene oxidation opens a new window in the application of organic super-molecules to solar cells.

  3. Plumbing the brain drain.

    PubMed Central

    Saravia, Nancy Gore; Miranda, Juan Francisco

    2004-01-01

    Opportunity is the driving force of migration. Unsatisfied demands for higher education and skills, which have been created by the knowledge-based global economy, have generated unprecedented opportunities in knowledge-intensive service industries. These multi-trillion dollar industries include information, communication, finance, business, education and health. The leading industrialized nations are also the focal points of knowledge-intensive service industries and as such constitute centres of research and development activity that proactively draw in talented individuals worldwide through selective immigration policies, employment opportunities and targeted recruitment. Higher education is another major conduit of talent from less-developed countries to the centres of the knowledge-based global economy. Together career and educational opportunities drive "brain drain and recirculation". The departure of a large proportion of the most competent and innovative individuals from developing nations slows the achievement of the critical mass needed to generate the enabling context in which knowledge creation occurs. To favourably modify the asymmetric movement and distribution of global talent, developing countries must implement bold and creative strategies that are backed by national policies to: provide world-class educational opportunities, construct knowledge-based research and development industries, and sustainably finance the required investment for these strategies. Brazil, China and India have moved in this direction, offering world-class education in areas crucial to national development, such as biotechnology and information technology, paralleled by investments in research and development. As a result, only a small proportion of the most highly educated individuals migrate from these countries, and research and development opportunities employ national talent and even attract immigrants. PMID:15375451

  4. Plumbing the brain drain.

    PubMed

    Saravia, Nancy Gore; Miranda, Juan Francisco

    2004-08-01

    Opportunity is the driving force of migration. Unsatisfied demands for higher education and skills, which have been created by the knowledge-based global economy, have generated unprecedented opportunities in knowledge-intensive service industries. These multi-trillion dollar industries include information, communication, finance, business, education and health. The leading industrialized nations are also the focal points of knowledge-intensive service industries and as such constitute centres of research and development activity that proactively draw in talented individuals worldwide through selective immigration policies, employment opportunities and targeted recruitment. Higher education is another major conduit of talent from less-developed countries to the centres of the knowledge-based global economy. Together career and educational opportunities drive "brain drain and recirculation". The departure of a large proportion of the most competent and innovative individuals from developing nations slows the achievement of the critical mass needed to generate the enabling context in which knowledge creation occurs. To favourably modify the asymmetric movement and distribution of global talent, developing countries must implement bold and creative strategies that are backed by national policies to: provide world-class educational opportunities, construct knowledge-based research and development industries, and sustainably finance the required investment for these strategies. Brazil, China and India have moved in this direction, offering world-class education in areas crucial to national development, such as biotechnology and information technology, paralleled by investments in research and development. As a result, only a small proportion of the most highly educated individuals migrate from these countries, and research and development opportunities employ national talent and even attract immigrants.

  5. High-Speed Programming Not-OR Flash Memory Cells With Titanium Disilicide Drain

    NASA Astrophysics Data System (ADS)

    Kim, Kyeong-Rok; Dal Kwack, Kae; Kim, Tae Whan

    2008-08-01

    A Not-OR (NOR) flash memory cell using a titanium disilicide (TiSi2) drain was designed to increase programming speed and driving current. This NOR flash memory cell with a TiSi2 drain was proposed on the basis of the fundamental structure of conventional NOR flash memory cells with a length of 90 nm. The programming speed and driving current of the NOR flash memory cell with a TiSi2 drain were simulated using T-SUPREM4 and MEDICI. The simulation results showed that the heavily doped carriers existing in the TiSi2 drain can be used to increase the programming speed of the NOR flash memory cell and that a decrease in source/drain series resistance utilizing the silicide in the NOR flash memory cell with a TiSi2 drain helps increase driving current density.

  6. Erbium and nitrogen co-doped SrTiO{sub 3} with highly visible light photocatalytic activity and stability by solvothermal synthesis

    SciTech Connect

    Xu, Jing; Wei, Yuelin; Huang, Yunfang; Wang, Jing; Zheng, Xuanqing; Sun, Zhixian; Wu, Ying; Tao, Xinling; Fan, Leqing; Wu, Jihuai

    2015-10-15

    Highlights: • Er/N co-doped SrTiO{sub 3} was prepared by a solvothermal process at low temperature. • The co-doping induces the band gap narrowing and prominent absorbance in visible light region. • The samples show excellent catalytic activity and stability under visible light irradiation. - Abstract: Erbium–nitrogen co-doped SrTiO{sub 3} photocatalysts have been synthesized by a facile solvothermal method. The resulting samples were analyzed by FE-SEM, XRD, BET-surface area and UV–vis. The UV–vis absorption spectra of these powders indicated that erbium–nitrogen co-doped SrTiO{sub 3} possessed stronger absorption bands in the visible light region in comparison with that of pure SrTiO{sub 3}. The occurrence of the erbium–nitrogen co-doped cubic SrTiO{sub 3} induced the higher photocatalytic activities for the degradation of methyl orange (MO) under irradiation by ultraviolet light and visible light, respectively, being superior to that of pure SrTiO{sub 3} and commercial TiO{sub 2} (P-25) powders. In addition, the Er–N co-doped SrTiO{sub 3} (initial molar ratios of Sr/Er/N = 1:0.015:0.1, designated as S5) sample showed the best photocatalytic activity with the degradation rate as high as 98% after 30 min under the visible light irradiation. After five cycles, the photocatalytic activity of the S5 catalyst showed no significant decrease, which indicated that the photocatalysts were stable under visible light irradiation.

  7. Sol-gel deposited gallium-doped zinc oxide electrode for polymer light-emitting diode applications

    NASA Astrophysics Data System (ADS)

    Kim, Donghyun; Ha, Jaeheung; Lee, Changhee; Hong, Yongtaek

    2012-09-01

    We have made a sol-gel deposited gallium-doped zinc oxide (GZO) film as a transparent conductive anode in polymer light-emitting diode (PLED) applications. The GZO films were obtained by spin-coating GZO precursor solutions followed by consecutive thermal annealing in the air and in the hydrogen-rich atmosphere. The resistance of GZO film was reduced to ~100 Ω/□ after thermal annealing in the hydrogen environment. Its surface roughness was sufficiently low (1.159 nm RMS) for depositing other polymer layers. We have fabricated PLEDs with quartz substrate / solution-processed GZO electrode (anode) / PEDOT:PSS (HITL) / SPG-01T (Green polymer light-emitting material purchased from Merck, EML) / Ca (EIL) / Al (Cathode). The fabricated devices showed current efficiency of 3.06 cd/A and power efficiency of 1.25 lm/W at luminance of 1000 cd/m2.

  8. Investigation of light induced effect on density of states of Pb doped CdSe thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdish; Singh, Baljinder; Tripathi, S. K.

    2016-05-01

    Thin films of Pb doped CdSe are deposited on the glass substrates by thermal evaporation technique using inert gas condensation method. The prepared thin films are light soaked under vacuum of 2×10-3 mbar for two hour. The absorption coefficient in the sub-band gap region has been studied using Constant Photocurrent Method (CPM). The absorption coefficient in the sub-band gap region follows an exponential Urbach tail. The value of Urbach energy and number density of defect states have been calculated from the absorption coefficient in the sub-band gap region and found to increase after light soaking treatment. The energy distribution of the occupied density of states below Fermi level has been evaluated using derivative procedure of the absorption coefficient.

  9. Novel rare earth ions-doped oxyfluoride nano-composite with efficient upconversion white-light emission

    NASA Astrophysics Data System (ADS)

    Chen, Daqin; Wang, Yuansheng; Yu, Yunlong; Huang, Ping; Weng, Fangyi

    2008-10-01

    Transparent SiO 2-Al 2O 3-NaF-YF 3 bulk nano-composites triply doped with Ho 3+, Tm 3+ and Yb 3+ were fabricated by melt-quenching and subsequent heating. X-ray diffraction and transmission electron microscopy measurements demonstrated the homogeneous precipitation of the β-YF 3 crystals with mean size of 20 nm among the glass matrix, and rare earth ions were found to partition into these nano-crystals. Under single 976 nm laser excitation, intense red, green and blue upconversion emissions were simultaneously observed owing to the successive energy transfer from Yb 3+ to Ho 3+ or Tm 3+. Various colors of luminescence, including bright perfect white light, can be easily tuned by adjusting the concentrations of the rare earth ions in the material. The overall energy efficiency of the white-light upconversion was estimated to be about 0.2%.

  10. Photocatalytic comparison of Cu- and Ag-doped TiO{sub 2}/GF for bioaerosol disinfection under visible light

    SciTech Connect

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2015-12-15

    Photocatalysts, TiO{sub 2}/glass fiber (TiO{sub 2}/GF), Cu-doped TiO{sub 2}/glass fiber (Cu–TiO{sub 2}/GF) and Ag-doped TiO{sub 2}/glass fiber (Ag–TiO{sub 2}/GF), were synthesized by a sol–gel method. They were then used to disinfect Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in bioaerosols under visible light irradiation. TiO{sub 2}/GF did not show any significant disinfection effect. Both Cu and Ag acted as intermediate agents to enhance separation efficiency of electron–hole pairs of TiO{sub 2}, leading to improved photocatalytic activity of Cu–TiO{sub 2}/GF and Ag–TiO{sub 2}/GF under visible light. Cu in Cu–TiO{sub 2}/GF acted as a defective agent, increasing the internal quantum efficiency of TiO{sub 2}, while Ag in Ag–TiO{sub 2}/GF acted as a sensitive agent, enhancing the transfer efficiency of the electrons generated. The highest disinfection efficiencies of E. coli and S. aureus by Cu–TiO{sub 2}/GF were 84.85% and 65.21%, respectively. The highest disinfection efficiencies of E. coli and S. aureus by Ag–TiO{sub 2}/GF were 94.46% and 73.12%, respectively. Among three humidity conditions – 40±5% (dry), 60±5% (moderate), and 80±5% (humid) – the moderate humidity condition showed the highest disinfection efficiency for both E. coli and S. aureus. This study also showed that a Gram-negative bacterium (E. coli) were more readily disinfected by the photocatalysts than a Gram-positive bacterium (S. aureus). - Graphical abstract: Electron–hole pair separation mechanism of a metal-doped TiO{sub 2} system.

  11. Modification of Blue LED using Organic-Inorganic Hybrid Polymer Doped with Nile Red for Artificial Lighting of Photosynthesis

    NASA Astrophysics Data System (ADS)

    Syakir, Norman; Syarifudin, Fahmi; Hidayat, Sahrul; Fitrilawati

    2017-07-01

    The photosynthesis process of chlorophyll absorbs only the light with wavelength in the blue and red ranges. The absorption peak of the chlorophyll-A is at 428 nm and 660 nm, while absorption peak of chlorophyll-B is at 453 nm and 643 nm. We report the modification of blue LED using hybrid polymer doped with Nile Red. In order to match the total absorption spectra of chlorophyll-A and chlorophyll-B, the emission spectrum of the modified blue LED was taken out by using the wavelength conversion material. We modified the blue LED by covering the blue LED of 450 nm as excitation source with precursor of red wavelength conversion material. The red wavelength conversion material was prepared by doped precursor of TMSPMA hybrid polymer with organic phosphor of Nile Red. The precursor of hybrid polymer was synthesized using sol-gel process and then it was doped with 0.1% Nile Red. In order to freeze the precursor of these conversion material, we employed UV photopolymerization process. The modified blue LED has two emission peaks, which are at 448 nm (blue emission) and at 651 nm (red emission). The optimum spectrum profile of the modified blue LED has similar range as the total absorption spectra of chlorophyll-A and chlorophyll-B that obtain using Nile Red with the mass of 2.9 μg and the driven current of 60 mA. This result has a potential application for the artificial lighting in the photosynthesis process of horticultures at indoor plantation.

  12. Photocatalytic Self-Doped SnO2-x Nanocrystals Drive Visible-Light-Responsive Color Switching.

    PubMed

    Han, Dan; Jiang, Baolai; Feng, Ji; Yin, Yadong; Wang, Wenshou

    2017-06-26

    Visible-light-responsive reversible color-switching systems are attractive to many applications because visible light has superior penetration and causes far less damage to organic molecules than UV. Herein, we report that self-doping of SnO2-x nanocrystals with Sn(2+) red-shifts their absorption to the visible region and simultaneously produces oxygen vacancies, which can effectively scavenge photogenerated holes and thus enable the color switching of redox dyes using visible light. Wavelength-selective switching can also be achieved by coupling the photocatalytic activity of the SnO2-x NCs with the color-switching kinetics of different redox dyes. The fast light response enables the further fabrication of a solid film that can be repeatedly written on using a visible laser pen or projection printing through a photomask. This discovery represents a big step forward towards practical applications, especially in areas in which safety issues and photodamage by UV light are of concern. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. A facile fabrication of nitrogen-doped electrospun In2O3 nanofibers with improved visible-light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Lu, Na; Shao, Changlu; Li, Xinghua; Miao, Fujun; Wang, Kexin; Liu, Yichun

    2017-01-01

    Semiconductor photocatalysis demonstrates to be an effective approach for eliminating most types of environment contaminants and for producing hydrogen. Herein, a facile synthesis route combining electrospinning technique and thermal treatment method under NH3 atmosphere has been presented as a straightforward protocol for the fabrication of nitrogen-doped In2O3 (N-In2O3) nanofibers, the nitrogen content of which can be well controlled by adjusting the annealing temperature. Photocatalytic tests show that the N-In2O3 nanofibers demonstrate an improved degradation rate of Rhodamine B (RB) compared with pure In2O3 nanofibers under visible-light irradiation. This can be attributed to the nitrogen atom introducing at interstitial sites as well as the generation of oxygen vacancy on the surface of In2O3 nanofibers, resulting in the enhanced utilization of visible light for the N-In2O3 nanofibers. Furthermore, the obtained N-In2O3 nanofibers with the advantage of ultra-long one-dimensional nanostructures can be recycled several times by facile sedimentation and hence present almost no decrease in photocatalytic activity indicative of a well regeneration capability. Therefore, the as-fabricated nitrogen-doped In2O3 nanofibers as a promising photocatalyst present good photocatalytic degradation of organic pollutant in waste water for practical application.

  14. Carbon wrapped and doped TiO2 mesoporous nanostructure with efficient visible-light photocatalysis for NO removal

    NASA Astrophysics Data System (ADS)

    He, Di; Li, Yongli; Wang, inshu; Wu, Junshu; Yang, Yilong; An, Qier

    2017-01-01

    Carbon wrapped and doped mesoporous anatase TiO2 nanocrystals were prepared by a hydrothermal approach in acetic acid aqueous containing chitosan. A designed post-thermal treatment was employed to enhance the incorporation between carbon and TiO2. After hydrothermal process, mesoporous anatase TiO2 formed with wrapped by a few layers of carbon shell. Here chitosan was used as not only the template for the formation of mesopores, but also the carbon source toward the carbon layers coating. Furthermore, chitosan provided doping element into TiO2 lattice and induced to form Tisbnd C bond which caused Ti(III) with oxygen vacancies. The Ti(III)-oxygen vacancy are partly responsible for visible-light response and high photocatalytic activity, which can accelerate electron transfer thus inhibit photogenerated charge recombination. The photocatalytic activity was evaluated using photo-oxidation of gaseous NO under visible light irradiation as the probe reaction. In the optimum result, 71% of NO with starting concentration at ppb level was photo-degraded. Our results also showed that the photogenerated electrons played a key role in photodegradation of NO, as a result, the environmental humidity level had a negligible effect on the photocatalysis.

  15. Characterization of the transport properties of channel delta-doped structures by light-modulated Shubnikov-de Haas measurements

    NASA Technical Reports Server (NTRS)

    Mena, R. A.; Schacham, S. E.; Haugland, E. J.; Alterovitz, S. A.; Young, P. G.; Bibyk, S. B.; Ringel, S. A.

    1995-01-01

    The transport properties of channel delta-doped quantum well structures were characterized by conventional Hall effect and light-modulated Shubnikov-de Haas (SdH) effect measurements. The large number of carriers that become available due to the delta-doping of the channel, leads to an apparent degeneracy in the well. As a result of this degeneracy, the carrier mobility remains constant as a function of temperature from 300 K down to 1.4 K. The large amount of impurity scattering, associated with the overlap of the charge carriers and the dopants, resulted in low carrier mobilities and restricted the observation of the oscillatory magneto-resistance used to characterize the two-dimensional electron gas (2DEG) by conventional SdH measurements. By light-modulating the carriers, we were able to observe the SdH oscillation at low magnetic fields, below 1.4 tesla, and derive a value for the quantum scattering time. Our results for the ratio of the transport and quantum scattering times are lower than those previously measured for similar structures using much higher magnetic fields.

  16. Enhanced visible light photocatalytic activity of copper-doped titanium oxide-zinc oxide heterojunction for methyl orange degradation

    NASA Astrophysics Data System (ADS)

    Dorraj, Masoumeh; Alizadeh, Mahdi; Sairi, Nor Asrina; Basirun, Wan Jefrey; Goh, Boon Tong; Woi, Pei Meng; Alias, Yatimah

    2017-08-01

    A novel Cu-doped TiO2 coupled with ZnO nanoparticles (Cu-TiO2/ZnO) was prepared by sol-gel method and subsequent precipitation for methyl orange (MO) photodegradation under visible light irradiation. The compositions and shapes of the as-prepared Cu-TiO2/ZnO nanocomposites were characterized by photoluminescence spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, UV-vis diffuse reflectance spectra and Brunauer-Emmett-Teller adsorption isotherm techniques. The Cu-TiO2/ZnO nanocomposites showed considerably higher photocatalytic activity for MO removal from water under visible light irradiation than that of single-doped semiconductors. The effects of Cu-TiO2 and ZnO mass ratios on the photocatalytic reaction were also studied. A coupling percentage of 30% ZnO exhibited the highest photocatalytic activity. The enhanced photocatalytic activity of the Cu-TiO2/ZnO nanocomposites was mainly attributed to heterojunction formation, which allowed the efficient separation of photoinduced electron-hole pairs at the interface. Moreover, these novel nanocomposites could be recycled during MO degradation in a three-cycle experiment without evident deactivation, which is particularly important in environmental applications.

  17. High-performance quantum dot light-emitting diodes with hybrid hole transport layer via doping engineering.

    PubMed

    Huang, Qianqian; Pan, Jiangyong; Zhang, Yuning; Chen, Jing; Tao, Zhi; He, Chao; Zhou, Kaifeng; Tu, Yan; Lei, Wei

    2016-11-14

    Here, we report on the hybrid hole transport materials 4,4'-bis-(carbazole-9-yl)biphenyl (CBP) or poly-N-vinylcarbazole (PVK) doped into poly(4-butyl-phenyl-diphenyl-amine) (Poly-TPD) as the hybrid hole transport layer (HTL) to tailor the energy band alignment between hole injection layer (HIL) and quantum dot (QD) light emitting layer in order to realize efficient quantum dot light emitting diodes (QLEDs) in all solution-processed fabrication. Compared to the pristine Poly-TPD based device, it is found that the electroluminescence (EL) performance of QLEDs can be significantly improved by 1.5 fold via addition of CBP into Poly-TPD, which can be attributed to the lowered highest occupied molecular orbital (HOMO) level of Poly-TPD to reduce the energy barrier between HTL and valance band (VB) of QDs. Thus, after doping small molecules into polymer under optimized proportion (Poly-TPD:CBP = 2:1 by weight), the hole transport rate can be balanced, facilitating the carrier injection from HTL to QDs and enhancing the efficiency of QLEDs. As a result, a maximum luminance, a maximum current efficiency and a maximum power efficiency of 7600 cd/m2, 5.41 cd/A and 4.25 lm/W can be obtained based on this variety of hybrid HTL employed QLEDs.

  18. Improved power efficiency in phosphorus doped n-a-SiNxOy/p-Si heterojunction light emitting diode

    NASA Astrophysics Data System (ADS)

    Lin, Zewen; Chen, Kunji; Zhang, Pengzhan; Xu, Jun; Li, Wei; Yang, Huafeng; Huang, Xinfan

    2017-02-01

    The higher up to 60% internal quantum efficiency of photoluminescence (PL) from amorphous silicon oxynitride (a-SiNxOy) films has been reported in our previous work. In present work, the improved power efficiency visible light emitting diode (LED) has been realized based on phosphorus doped n-a-SiNxOy/p-Si heterojunction structure, which is at least three times higher than that of ITO/a-SiNxOy/p-Si (called MIS) LED. The n-a-SiNxOy films were doped by using phosphine (PH3) gas during the deposition by plasma enhanced chemical vapor deposition technique and the electron concentration is about 2.4 × 1015 cm-3 at room temperature obtained from Hall-effect measurements. The light emitting (electroluminescence (EL)) peak energy is coincided with that of PL of a-SiNxOy, which suggests that the EL emission is also originated from the radiative recombination via N-Si-O bonding defect states in n-a-SiNxOy layers. The transport mechanism and optical performance of the device have been investigated with the characteristics of current-voltage (I-V) and light output-voltage (L-V), in terms of the energy band diagram of n-a-SiNxOy/p-Si heterojunction structure. The power law like L ˜ Im of light output-current (L ˜ I) characteristic in n-a-SiNxOy/p-Si heterojunction has also been observed, which exhibits a superlinear behaviour with a slope of 1.35 in the low current range and becomes almost linear with a slope of 1.05 in the high current range, due to the saturation of nonradiative recombination centers.

  19. Measurement and Comparison of the Light Output of Ni-doped 6LiF/ZnS for Use in Neutron Multiplicity Counting

    SciTech Connect

    Behling, Richard S.; Bliss, Mary; Cowles, Christian C.; Kouzes, Richard T.; Lintereur, Azaree; Robinson, Sean M.; Siciliano, Edward R.; Stave, Sean C.; Wang, Zheming

    2016-10-06

    Abstract–Alternatives to 3He for neutron detection have recently become attractive for safeguards applications. Pacific Northwest National Laboratory is developing a neutron multiplicity counter that is based on 6LiF/ZnS. Some of the properties of this material, such as the scintillation light decay time, can be tuned by doping the material with a small amount of nickel. This doping affects other properties of the material, in particular the time dependence of the scintillation light output. To determine whether the nickel-doped or undoped 6LiF/ZnS material would better suit the neutron multiplicity counter system, a series of experiments compared the use of undoped 6LiF/ZnS and a Ni-doped variant using both small samples and full-scale detectors made using the two materials. Both materials were manufactured by Eljen Technology of Sweetwater, Texas. The Ni-doped variant produced less light than the undoped material and had a shorter decay time. For all choices of detection threshold above the electronic noise, the decrease in light output did not affect the detection efficiency of the system.

  20. Comparative Photocatalytic Degradation of Monoazo and Diazo Dyes Under Simulated Visible Light Using Fe3+/C/S doped-TiO2 Nanoparticles.

    PubMed

    Anku, William Wilson; Oppong, Samuel Osei-Bonsu; Shukla, Sudheesh Kumar; Govender, Poomani Penny

    2016-01-01

    This research work delved into the photocatalytic degradation of monoazo dye (methyl orange) and diazo dye (congo red) in aqueous solution using Fe3+/C/S-doped TiO2 nanocomposites. The nanocomposites were synthesised through sol-gel method and characterized using XRD, FTIR, SEM, TEM, EDX, BET and UV-Vis. Photocatalytic degradation of the dyes was monitored under simulated visible light using pristine TiO2, C/S/doped-TiO2 and Fe3+/C/S doped-TiO2 with varying concentrations of Fe3+. The influence of catalyst doping, solution pH, and light intensity were also examined. Doping TiO2 with Fe3+/C/S caused reduction in its band gap value with the resultant improvement in its visible light activity. The photocatalytic efficiency of the catalysts is given as follows: TiO2 < C/S/TiO2 < Fe3+/C/S-TiO2 with Fe3+/C/S-TiO2 (0.3% Fe3+) as the best performing photocatalyst. The monoazo dye experienced higher degradation efficiency than the diazo dye. Degradation of the azo dyes was observed to decrease with increasing pH from 2 to 12. Increased visible light intensity enhanced the photodegradation efficiency of the dye. Dye decolourization was observed to be faster than its mineralization.

  1. Effective visible light-active boron and europium co-doped BiVO4 synthesized by sol-gel method for photodegradion of methyl orange.

    PubMed

    Wang, Min; Che, Yinsheng; Niu, Chao; Dang, Mingyan; Dong, Duo

    2013-11-15

    Eu-B co-doped BiVO4 visible-light-driven photocatalysts have been synthesized using the sol-gel method. The resulting materials were characterized by a series of joint techniques, including XPS, XRD, SEM, BET, and UV-vis DRS analyses. Compared with BiVO4 and B-BiVO4 photocatalysts, the Eu-B-BiVO4 photocatalysts exhibited much higher photocatalytic activity for methyl orange (MO) degradation under visible light irradiation. The optimal Eu doping content is 0.8 mol%. It was revealed that boron and europium were doped into the lattice of BiVO4 and this led to more surface oxygen vacancies, high specific surface areas, small crystallite size, a narrower band gap and intense light absorbance in the visible region. The doped Eu(III) cations can help in the separation of photogenerated electrons. The synergistic effects of boron and europium in doped BiVO4 were the main reason for improving visible light photocatalytic activity. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Synergistic Effects of Sm and C Co-Doped Mixed Phase Crystalline TiO2 for Visible Light Photocatalytic Activity

    PubMed Central

    Peng, Fuchang; Gao, Honglin; Zhang, Genlin; Zhu, Zhongqi; Zhang, Jin; Liu, Qingju

    2017-01-01

    Mixed phase TiO2 nanoparticles with element doping by Sm and C were prepared via a facile sol-gel procedure. The UV-Vis light-diffuse reflectance spectroscopy analysis showed that the absorption region of co-doped TiO2 was shifted to the visible-light region, which was attributed to incorporation of samarium and carbon into the TiO2 lattice during high-temperature reaction. Samarium effectively decreased the anatase-rutile phase transformation. The grain size can be controlled by Sm doping to achieve a large specific surface area useful for the enhancement of photocatalytic activity. The photocatalytic activities under visible light irradiation were evaluated by photocatalytic degradation of methylene blue (MB). The degradation rate of MB over the Sm-C co-doped TiO2 sample was the best. Additionally, first-order apparent rate constants increased by about 4.3 times compared to that of commercial Degusssa P25 under the same experimental conditions. Using different types of scavengers, the results indicated that the electrons, holes, and •OH radicals are the main active species for the MB degradation. The high visible-light photocatalytic activity was attributed to low recombination of the photo-generated electrons and holes which originated from the synergistic effect of the co-doped ions and the heterostructure. PMID:28772569

  3. Mechanism of photocatalytic activities in Cr-doped SrTiO3 under visible-light irradiation: an insight from hybrid density-functional calculations.

    PubMed

    Reunchan, Pakpoom; Umezawa, Naoto; Ouyang, Shuxin; Ye, Jinhua

    2012-02-14

    We used hybrid density-functional calculations to clarify the effect of substituting chromium for titanium (Cr(Ti)) on photocatalytic activities of Cr-doped SrTiO(3). A singly negative Cr(Ti)⁻, which is relevant to a lower oxidation state of Cr, is advantageous for the visible light absorption without forming electron trapping centers, while other charge states are inactive for the photocatalytic reaction. Stabilizing the desirable charge state (Cr(Ti)⁻) is feasible by shifting the Fermi level towards the conduction band. Our theory sheds light on the photocatalytic properties of metal-doped semiconductors.

  4. A novel approach for enhanced visible light activity in doped nanosize titanium dioxide through the excitons trapping

    SciTech Connect

    Jaimy, Kanakkanmavudi B.; Baiju, K.V.; Ghosh, Swapankumar; Warrier, K.G.K.

    2012-02-15

    Titanium dioxide doped with iron oxide (0-10 mol%) has been synthesized by an aqueous sol-gel method. The extent of phase transformation is higher in presence of up to 1 mol% of Fe{sup 3+} ions in doped titania. A further increase in Fe{sup 3+} content was found to decrease the phase transformation. A composition which contains {approx}90% rutile and the remaining anatase phase shows the highest photocatalytic activity. Even though surface area values are dramatically decreased by the modification of TiO{sub 2} by Fe{sup 3+} doping, crystallinity plays a major role in photocatalytic activity enhancement. UV-vis reflectance spectra indicate a red-shift in band gap energy and thus an enhanced photoactivity in visible light, suitable for application in photodegradation of toxic industrial effluents as well as other organic contaminants, is achieved. Low concentrations of Fe{sup 3+} ions act as excitons trapping centers, while higher concentrations act as recombination centers. The synergy between the rutile-anatase ratios and optimum amount of Fe{sup 3+} ions improve the interfacial charge transfer and trapping which enhanced the photochemical degradation of MB dye. The Fe{sup 3+} doped TiO{sub 2} composition has the highest photoactivity, having an apparent rate constant of 11.1 Multiplication-Sign 10{sup -3} min{sup -1}, which is much higher than that of commercial P25 Degussa titania (6.03 Multiplication-Sign 10{sup -3} min{sup -1}). - Graphical abstract: Model explaining the transfer and trapping of e{sup -}/h{sup +} pairs in mixed phase titania by Fe{sup 3+} ions suggests the reason for the increased lifetime of e{sup -}/h{sup +} pairs and enhanced photocatalytic activity. Highlights: Black-Right-Pointing-Pointer An aqueous sol-gel method for the preparation of doped TiO{sub 2} is being reported. Black-Right-Pointing-Pointer High photocatalytic activity and simplicity are the novelty of this work. Black-Right-Pointing-Pointer Enhanced activity is explained by the

  5. A systematic study on visible-light N-doped TiO2 photocatalyst obtained from ethylenediamine by sol-gel method

    NASA Astrophysics Data System (ADS)

    Li, Hui; Hao, Yubao; Lu, Haiqiang; Liang, Liping; Wang, Yuanyang; Qiu, Jianhao; Shi, Xianchao; Wang, Ying; Yao, Jianfeng

    2015-07-01

    N-doped titania is prepared using ethylenediamine as the nitrogen source by a sol-gel method. The preparation conditions, such as the volume ratio of ethylenediamine to sol, and the heat temperature on the nitrogen doping are systematically examined. UV results indicate the N-doped TiO2 catalysts have enhanced absorption in the visible light region, and exhibit high activities on the visible light photocatalytic reactions to the hydrogen production and methyl orange degradation. X-ray diffraction (XRD) and FT-IR results reveal that N species have been incorporated into the TiO2 lattice at a high N-doping level. N-doped titania prepared with an ethylenediamine to sol volume ratio of 1:1 and sintering temperature of 500 °C performed the highest hydrogen production rate (2.98 mmol g-1 h-1) and best methyl orange degradation performance. A conceivable structure change of N-doped TiO2 sintered at different temperature was proposed.

  6. Fabrication of the C-N co-doped rod-like TiO{sub 2} photocatalyst with visible-light responsive photocatalytic activity

    SciTech Connect

    Li, Liang-Hai; Lu, Juan; Wang, Zuo-Shan; Yang, Lu; Zhou, Xiu-Feng; Han, Lu

    2012-06-15

    Highlights: ► Novel synthesis of C-N co-doped TiO{sub 2}. ► Self-assembly of C-N co-doped TiO{sub 2} nanorods by nanoparticles. ► Excellent photocatalytic efficiency. -- Abstract: The C-N co-doped TiO{sub 2} nanorods were synthesized by the vapor transport method of water molecules, and urea was used as the carbon and nitrogen source. The samples were characterized by X-ray diffraction and photoelectron spectroscopy analysis. The scanning electron microscope images showed that as-prepared TiO{sub 2} powders were nanorods, which were formed by the stacking of nanoparticles with a uniform size around 40 nm. The degradation of methylene blue with the prepared nanorods demonstrated the photocatalytic activities of TiO{sub 2} under visible light are improved by doping with C and N elements. The main reasons were discussed: doping with C and N elements could enhance the corresponding visible-light absorption of TiO{sub 2}. On the other hand, doping C and N could create more oxygen vacancies in the TiO{sub 2} crystals, which could capture the photogenerated electrons more effectively. Thus, more photogenerated holes could be left to improve the photocatalytic activity of TiO{sub 2}.

  7. UV light sensing properties of Sm doped vertically aligned ZnO nanorod arrays

    SciTech Connect

    Kumar, D. Ranjith; Ranjith, K. S.; Rajendrakumar, R. T.

    2015-06-24

    Samarium doped ZnO nanorods were grown on silicon substrate by using vapor phase transport method (VPT) with the growth temperature of 950°C. The synthesized nanorods were characterized by XRD, field emission scanning electron microscopy, Raman spectra, and photocurrent measurements. The XRD result revealed that Sm was successfully doped into lattice plane of hexagonal ZnO nanorods. The FESEM result confirms the pure ZnO has nanorod like morphology with an average diameter and length of 130nm and 10µm respectively. The above observation is supported by the Micro-Raman spectroscopy result. The photocurrent in the visible region has been significantly enhanced due to deposition of Sm on the surface of the ZnO nanorods. Sm acts as a visible sensitizer because of its lower band gap compared to ZnO.

  8. High-stability polymer optical fiber with Rhodamine-doped cladding for fiber light systems

    NASA Astrophysics Data System (ADS)

    Jaramillo-Ochoa, L.; Narro-García, R.; Ocampo, M. A.; Quintero-Torres, R.

    2016-09-01

    In this work, the photodegradation of a polymer optical fiber with Rhodamine doped cladding as a function of illumination time and excitation intensity is presented. To show the effect of photodegradation on different bulk geometries and environments, the photodegradation from a dye doped preform and a PMMA thick film is also evaluated. The reversible and the irreversible degradation of the florescent material were quantified under an established excitation scheme. To this purpose, a four-level system to model the photodegradation rates and its relation with the population of the states is presented and it is used to justify a possible underlying mechanism. The obtained results suggest an increase of one order of magnitude in the stability (lifetime) of the polymer optical fiber with respect to the preform or the thick film geometry stability.

  9. One-step synthesis, characterization, and visible light photocatalytic activity of pure and Zn-doped SnO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Madhan, D.; Rajkumar, P.; Rajeshwaran, P.; Sivarajan, A.; Sangeetha, M.

    2015-08-01

    A one-step microwave irradiation route was used to synthesize undoped and Zn-doped SnO2 nanoparticles for the first time. The morphologies, structures and optical properties of the as-prepared samples were characterized by X-ray powder diffraction, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy, UV-Vis spectra and photoluminescence spectra analysis. The results clearly revealed that both the pure and doped samples had a tetragonal rutile-type structure and a space group of P42/mnm have formed directly during the microwave irradiation process. FESEM studies illustrate that both the pristine and Zn-doped SnO2 form in spherical-shaped morphology with an average diameter around 41-32 nm, which is in good agreement with the average crystallite sizes calculated by Scherrer's formula. Optical studies reveal that both pristine and Zn-doped SnO2 direct transitions occur with the bandgap energies in the range of 3.43-3.26 eV. The photocatalytic activities of the pure and Zn-doped SnO2 samples were evaluated by the degradation of methylene blue rhodamine B in an aqueous solution under visible light irradiation. The photocatalytic activity and reusability of Zn (10 wt%)-doped SnO2 was much higher than that of the pure SnO2. The improvement mechanism by zinc doping was also discussed.

  10. Comparing Cr, and N only doping with (Cr,N)-codoping for enhancing visible light reactivity of TiO2

    SciTech Connect

    Li, Yuan; Wang, Wei; Qiu, Xiaofeng; Meyer III, Harry M; Paranthaman, Mariappan Parans; Eres, Gyula; Zhang, Zhenyu; Gu, Baohua

    2011-01-01

    The photoreactivity of titania (TiO2) nanoclusters with varying levels of N or Cr-doping, or (Cr,N)-codoping, was systematically investigated using photodegradation of methyl orange in aqueous suspensions. The shifting of the TiO2 absorption edge into the visible spectral region that is primarily attributable to band gap narrowing was found to be a reliable metric for estimating the photoreactivity of the doped nanoclusters. Compared to the weak response with undoped and N-doped TiO2, Cr-doping and (Cr, N)-codoping were found to significantly enhance photodegradation of methyl orange under visible light. The initial reaction rates increase from about 0 to above 1.6 10-2 min-1 when the doping concentration of Cr in TiO2 increases from 0 to 5%. In stark contrast, under UV irradiation, doping is not only ineffective but detrimental to the photoreactivity, and all doping including N or Cr only and (Cr, N)-codoping were found to reduce photoreactivity.

  11. Enhanced visible-light photocatalytic performance of electrospun carbon-doped TiO2/halloysite nanotube hybrid nanofibers.

    PubMed

    Jiang, Ling; Huang, Yunpeng; Liu, Tianxi

    2015-02-01

    In this work, the effects of halloysite nanotubes (HNTs) on the visible-light photocatalytic ability of electrospun carbon doped TiO2/HNT (C-TH) nanofibers have been explored. Structural and morphological investigations demonstrate that incorporation of HNTs into anatase C-TH hybrid nanofibers was easily achieved by using sol-gel processing combined with electrospinning approach, thus HNTs could be uniformly embedded in the electrospun nanofibers. The visible-light photocatalytic efficiency of C-TH hybrid on the degradation of methyl blue (MB) was greatly enhanced with the combination of moderate amount of HNTs (8%), which was 23 times higher than that of commercial anatase TiO2. Mechanism of the enhancing effect of HNTs has been explored by analyzing the dual-effect of adsorption and photocatalysis in various amounts of HNTs incorporated C-TiO2 nanofibers. With nanotubular structure and considerable adsorption ability, incorporated HNTs functioned as porogen agent in C-TH nanofibers. This simple incorporation approach increases the specific surface areas of nanofibers, which improves the mass transport of reactant into the nanofibers and the adsorption of visible-light by scattering, meanwhile may suppress the charge recombination and enhance photoinduced charge separation, thus efficiently enhancing visible-light photocatalytic performance of the C-TH hybrid nanofibers. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. White light generation from Dy3+-doped ZnO-B2O3-P2O5 glasses

    NASA Astrophysics Data System (ADS)

    Jayasimhadri, M.; Jang, Kiwan; Lee, Ho Sueb; Chen, Baojiu; Yi, Soung-Soo; Jeong, Jung-Hyun

    2009-07-01

    Dysprosium doped ZnO-B2O3-P2O5 (ZBP) glasses were prepared by a conventional melt quenching technique in order to study the luminescent properties and their utility for white light emitting diodes (LEDs). X-ray diffraction spectra revealed the amorphous nature of the glass sample. The present glasses were characterized by infrared and Raman spectra to evaluate the vibrational features of the samples. The emission and excitation spectra were reported for the ZBP glasses. Strong blue (484 nm) and yellow (574 nm) emission bands were observed upon various excitations. These two emissions correspond to the F49/2→H615/2 and F49/2→H613/2 transitions of Dy3+ ions, respectively. Combination of these blue and yellow bands gives white light to the naked eye. First time, it was found that ZnO-B2O3-P2O5 glasses efficiently emit white light under 400 and 454 nm excitations, which are nearly match with the emissions of commercial GaN blue LEDs and InGaN LED, respectively. CIE chromaticity coordinates also calculated for Dy3+: ZBP glasses to evaluate the white light emission.

  13. White-light-emitting long-lasting phosphorescence in Dy{sup 3+}-doped SrSiO{sub 3}

    SciTech Connect

    Kuang Jinyong; Liu Yingliang . E-mail: tliuyl@jnu.edu.cn; Zhang Jianxian

    2006-01-15

    We report on a luminescent phenomenon in Dy{sup 3+}-doped SrSiO{sub 3} long-lasting phosphor. After irradiation by a 254-nm UV lamp for 5min, the Dy{sup 3+}-doped SrSiO{sub 3} phosphor emits white light-emitting long-lasting phosphorescence for more than 1h even after the irradiation source has been removed. Photoluminescence, long-lasting phosphorescence and thermoluminescence (TL) spectra are used to explain this phenomenon. Photoluminescence spectra reveal that the white light-emitting long-lasting phosphorescence originated from the two mixtures of Dy{sup 3+} characteristic luminescence, the 480-nm blue emission ({sup 4}F{sub 9/2}->{sup 6}H{sub 15/2}) and the 572-nm yellow emission ({sup 4}F{sub 9/2}->{sup 6}H{sub 13/2}). TL spectra shows that the introduction of Dy{sup 3+} ions into the SrSiO{sub 3} host produces a highly dense trapping level at 377K (0.59eV), which is responsible for the long-lasting phosphorescence at room temperature. A possible mechanism of the long-lasting phosphorescence based on the experimental results is proposed. It is considered that the long-lasting phosphorescence is due to persistent energy transfer from the electron traps to the Dy{sup 3+} ions, which creates the persistent luminescence of Dy{sup 3+} to produce the white light-emitting long-lasting phosphorescence.

  14. Role of vacancies, light elements and rare-earth metals doping in CeO2

    NASA Astrophysics Data System (ADS)

    Shi, H.; Hussain, T.; Ahuja, R.; Kang, T. W.; Luo, W.

    2016-08-01

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties.

  15. Doping effect on photoabsorption and charge-separation dynamics in light-harvesting organic molecule

    SciTech Connect

    Ohmura, Satoshi; Tsuruta, Kenji; Shimojo, Fuyuki; Nakano, Aiichiro

    2016-01-15

    Using ab-initio theoretical methods, we demonstrate possible enhancement of photo-conversion efficiency of an organic solar cell via intentional doping in molecular graphene-fullerene heterojunction [the hexabenzocoronene (HBC)-triethylene glycol (TEG)–C{sub 60} molecule]. Photoabsorption analysis indicates oxygen substitution into HBC leads to an extension of the spectra up to an infrared regime. A quantum-mechanical molecular dynamics simulation incorporating nonadiabatic electronic transitions reveals that a dissociated charge state (D{sup +} and A{sup -}) in the O-doped system is more stable than the pristine case due to the presence of an effective barrier by the TEG HOMO/LUMO level. We also find that oxygen doping in HBC enhances the intermolecular carrier mobility after charge separation. On the other hand, the pristine molecule undergoes rapid recombination between donor and acceptor charges at the interface. These analyses suggest that the graphene oxidation opens a new window in the application of organic super-molecules to solar cells.

  16. Role of vacancies, light elements and rare-earth metals doping in CeO2

    PubMed Central

    Shi, H.; Hussain, T.; Ahuja, R.; Kang, T. W.; Luo, W.

    2016-01-01

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties. PMID:27554285

  17. Role of vacancies, light elements and rare-earth metals doping in CeO2.

    PubMed

    Shi, H; Hussain, T; Ahuja, R; Kang, T W; Luo, W

    2016-08-24

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties.

  18. Samarium and Nitrogen Co-Doped Bi2 WO6 Photocatalysts: Synergistic Effect of Sm(3+) /Sm(2+) Redox Centers and N-Doped Level for Enhancing Visible-Light Photocatalytic Activity.

    PubMed

    Wang, Fangzhi; Li, Wenjun; Gu, Shaonan; Li, Hongda; Wu, Xue; Liu, Xintong

    2016-08-26

    Samarium and nitrogen co-doped Bi2 WO6 nanosheets were successfully synthesized by using a hydrothermal method. The crystal structures, morphology, elemental compositions, and optical properties of the prepared samples were investigated. The incorporation of samarium and nitrogen ions into Bi2 WO6 was proved by X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. UV/Vis diffuse reflectance spectroscopy indicated that the samarium and nitrogen co-doped Bi2 WO6 possessed strong visible-light absorption. Remarkably, the samarium and nitrogen co-doped Bi2 WO6 exhibited higher photocatalytic activity than single-doped and pure Bi2 WO6 under visible-light irradiation. Radical trapping experiments indicated that holes (h(+) ) and superoxide radicals ((.) O2 (-) ) were the main active species. The results of photoluminescence spectroscopy and photocurrent measurements demonstrated that the recombination rate of the photogenerated electrons and holes pairs was greatly depressed. The enhanced activity was attributed to the synergistic effect of the in-built Sm(3+) /Sm(2+) redox pair centers and the N-doped level. The mechanism of the excellent photocatalytic activity of Sm-N-Bi2 WO6 is also discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Enhancement in visible light-responsive photocatalytic activity by embedding Cu-doped ZnO nanoparticles on multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ahmad, M.; Ahmed, E.; Hong, Z. L.; Jiao, X. L.; Abbas, T.; Khalid, N. R.

    2013-11-01

    Copper doped ZnO nanoparticles embedded on multi-walled carbon nanotubes (CNTs) were successfully synthesized using a facile, nontoxic sol method. The resulting visible light-responsive Cu-doped ZnO/CNTs composites were characterized using powder X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), transmission electron microscope (TEM), scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and Brunauer Emmett Teller (BET) surface area analyzer. Optical properties of Cu-doped ZnO/CNTs nanocomposites, studied using UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy (PL), which exhibited extended light absorption in visible light region and possessed better charge separation capability, respectively as compared to Cu-doped ZnO, pure ZnO and ZnO/CNTs composite. The photocatalytic activity was tested by degradation of methyl orange (MO) dye under visible light irradiation. The results demonstrated that Cu-doped ZnO/CNTs nanocomposites effectively bleached out MO, showing an impressive photocatalytic enhancement over ZnO, commercial ZnO, Cu-doped ZnO nanoparticles and ZnO/CNTs nanocomposites. Chemical oxygen demand (COD) of textile wastewater was also measured before and after the photocatalysis experiment under sunlight to evaluate the mineralization of wastewater. The significant decrease in COD of the treated effluent revealed a complete destruction of the organic molecules along with color removal. This dramatically enhanced photoactivity of nanocomposite photocatalysts was attributed to greater adsorptivity of dyes, extended light absorption and increased charge separation efficiency due to excellent electrical properties of carbon nanotubes and the large surface area.

  20. N-doped TiO2 based visible light activated label-free photoelectrochemical biosensor for detection of Hg(2+) through quenching of photogenerated electrons.

    PubMed

    Han, Qianqian; Wang, Kewei; Xu, Lijun; Yan, Xiang; Zhang, Kunchi; Chen, Xing; Wang, Qinglin; Zhang, Lan; Pei, Renjun

    2015-06-21

    A novel photoelectrochemical (PEC) biosensor was fabricated based on N-doped TiO2 for the detection of Hg(2+) through the quenching of photogenerated electrons. The N-doped TiO2 was synthesized by a sol-gel method with urea and tetrabutyl titanate as the N and Ti sources. Compared with the undoped TiO2, the N-doped TiO2 showed an enhanced photocurrent response under visible light (λ > 420 nm). The sensing surface was functionalized with 5'-amino-modified T-rich oligonucleotides. The photoelectrochemical biosensor bound Hg(2+) on the surface by a highly specific T-Hg(2+)-T recognition. Hg(2+) on the surface of the N-doped TiO2 film withdrew the photogenerated electrons and decreased the recorded current signal. The dynamic linear range for Hg(2+) has been determined to be as low as 2-6 μM.

  1. Effects of emission layer doping on the spatial distribution of charge and host recombination rate density in organic light emitting devices: A numerical study

    SciTech Connect

    Li, Yanli; Zhou, Maoqing; Zheng, Tingcai; Yao, Bo; Peng, Yingquan

    2013-12-28

    Based on drift-diffusion theory, a numerical model of the doping of a single energy level trap in the emission layer of an organic light emitting device (OLED) was developed, and the effects of doping of this single energy level trap on the distribution of the charge density, the recombination rate density, and the electric field in single- and double-layer OLEDs were studied numerically. The results show that by doping the n-type (p-type) emission layer with single energy electron (hole) traps, the distribution of the recombination rate density can be tuned and shifted, which is useful for improvement of the device performance by reduced electrode quenching or for realization of desirable special functions, e.g., emission spectrum tuning in multiple dye-doped white OLEDs.

  2. Experimental verification of effects of barrier dopings on the internal electric fields and the band structure in InGaN/GaN light emitting diodes

    SciTech Connect

    Song, Jung-Hoon; Kim, Tae-Soo; Park, Ki-Nam; Lee, Jin-Gyu; Hong, Soon-Ku; Cho, Sung-Royng; Lee, Seogwoo; Whan Cho, Meoung

    2014-03-24

    We experimentally clarify the effects of barrier dopings on the polarization induced electric fields and the band structure in InGaN/GaN blue light emitting diodes. Both effects were independently verified by using electric field modulated reflectance and capacitance-voltage measurement. It is shown that the Si barrier doping does reduce the polarization induced electric field in the quantum wells. But the benefit of Si-doping is nullified by modification of the band structure and depletion process. With increased number of doped barriers, smaller number of quantum wells remains in the depletion region at the onset of the diffusion process, which can reduce the effective active volume and enhance the electron overflow.

  3. Solution-processed conjugated polymer organic p-i-n light-emitting diodes with high built-in potential by solution- and solid-state doping

    NASA Astrophysics Data System (ADS)

    Sivaramakrishnan, Sankaran; Zhou, Mi; Kumar, Aravind C.; Chen, Zhi-Li; Png, Rui-Qi; Chua, Lay-Lay; Ho, Peter K. H.

    2009-11-01

    Polymer p-i-n homojunction light-emitting diodes (LEDs) comprising p-doped poly(dioctylfluorene-alt-benzothiadiazole) (F8BT) hole-injection, intrinsic F8BT emitter, and n-doped F8BT electron-injection layers have been demonstrated. A thin F8BT film was photocrosslinked and bulk p-doped by nitronium oxidation, then overcoated with an F8BT layer which was then surface n-doped by contact printing with naphthalenide on an elastomeric stamp. These LEDs exhibit high built-in potential (Vbi=2.2 V), efficient bipolar injection, and greatly improved external electroluminescence efficiency compared to control devices without the p-i-n structure. A modulated photocurrent technique was used to measure this Vbi, which systematically improves with diode structure.

  4. Variation of the coordination environment and its effect on the white light emission properties in a Mn-doped ZnO-ZnS complex structure.

    PubMed

    Cheng, Yan; Chen, Rui; Feng, Haifeng; Hao, Weichang; Xu, Huaizhe; Wang, Yu; Li, Jiong

    2014-03-14

    Mn-doped ZnO-ZnS complex nanocrystals were fabricated through coating of dodecanethiol on Mn-doped ZnO nanocrystals. The relationship between the component of white light emission and the coordination environments of Mn-dopants were experimentally investigated. It was shown that Mn ions mainly formed Mn(3+)O6 octahedra in as prepared Mn-doped ZnO, while the Mn(3+) ions on the surface of ZnO transferred into Mn(2+) ions at the interface between ZnO and ZnS after dodecanethiol coating. The Mn(2+)S4 tetrahedron density and the orange emission intensity increased upon enhancing the dodecanethiol content. These results provide an alternative way to optimize the white emission spectrum from nanocrystals of Mn-doped ZnS-ZnO complex structures through modulation of the coordination environment of Mn ions.

  5. Solid-state chemical synthesis of rod-like fluorine-doped β-Bi2O3 and their enhanced photocatalytic property under visible light

    NASA Astrophysics Data System (ADS)

    Liang, Zhiting; Cao, Yali; Li, Yizhao; Xie, Jing; Guo, Nana; Jia, Dianzeng

    2016-12-01

    The pure β-Bi2O3 and fluorine-doped β-Bi2O3 rod-like microstructures were successfully prepared by a facile solid-state chemical reaction process. The composition, structure and morphology of the samples were determined by XRD, EDS, SEM, TEM, HRTEM, XPS and PL. Photocatalytic activities of all samples were investigated via the degradation of methyl orange (MO) under the irradiation of visible light. The fluorine-doped β-Bi2O3 rods exhibited higher photocatalytic activities than the pure β-Bi2O3 rod-like structures and commercial sample. The 82% MO can be degraded by the fluorine-doped β-Bi2O3 rods after irradiation for 2 h under visible light, which is 2-3 times higher than that of counterparts. The enhanced properties of the fluorine-doped samples attribute to their higher separation efficiency of electron-hole pairs and strong oxidation potential of valance band holes. The results show that the as-prepared rod-like fluorine-doped β-Bi2O3 materials are potential candidates for photocatalysts irradiated by visible light.

  6. Visible light driven mineralization of spiramycin over photostructured N-doped TiO2 on up conversion phosphors.

    PubMed

    Sacco, Olga; Vaiano, Vincenzo; Sannino, Diana; Ciambelli, Paolo

    2017-04-01

    A novel visible light-active photocatalyst formulation (NdT/OP) was obtained by supporting N-doped TiO2 (NdT) particles on up-conversion luminescent organic phosphors (OP). The photocatalytic activity of such catalysts was evaluated for the mineralization process of spiramycin in aqueous solution. The effect of NdT loading in the range 15-60wt.% on bulk and surface characteristics of NdT/OP catalysts was investigated by several chemico-physical characterization techniques. The photocatalytic performance of NdT/OP catalysts in the removal of spyramicin from aqueous solution was assessed through photocatalytic tests under visible light irradiation. Total organic carbon (TOC) of aqueous solution, and CO and CO2 gas concentrations evolved during the photodegradation were analyzed. A dramatic enhancement of photocatalytic activity of the photostructured visible active NdT/OP catalysts, compared to NdT catalyst, was observed. Only CO2 was detected in gas-phase during visible light irradiation, proving that the photocatalytic process is effective in the mineralization of spiramycin, reaching very high values of TOC removal. The photocatalyst NdT/OP at 30wt.% of NdT loading showed the highest photocatalytic activity (58% of TOC removed after 180min irradiation against only 31% removal after 300min of irradiation of NdT). We attribute this enhanced activity to the high effectiveness in the utilization of visible light through improved light harvesting and exploiting. OP particles act as "photoactive support", able to be excited by the external visible light irradiation, and reissue luminescence of wavelength suitable to promote NdT photomineralization activity. Copyright © 2016. Published by Elsevier B.V.

  7. Preparation and characterization of visible-light-driven TiO2 photocatalyst Co-doped with nitrogen and erbium.

    PubMed

    Chen, Guihua; Wang, Yong; Zhang, Juihui; Wu, Chenglin; Liang, Huading; Yang, Hui

    2012-05-01

    A series of nitrogen and erbium co-doped TiO2 photocatalyst was prepared by sol-hydrothermal method. The structure and properties of the photocatalyst were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra (DRS). The XRD and BET results showed that co-doping inhibited the increase of crystallite size and enlarged specific surface areas. XPS spectroscopy indicated nitrogen atoms were incorporated into TiO2 lattice, and erbium atoms mostly existed in the forms of Er2O3. A shift of the absorption edge to the lower energy and four absorption bands located at 654, 544, 524 and 489 nm attributed to the 4f transitions of 4I15/2 --> 4F2/9, 4I15/2 --> 4S3/2, 4I15/2 --> 2H11/2, 4I15/2 --> 4F7/2 of Er3+ were observed using DRS spectroscopy. The catalytic efficency was evaluated by the photocatalytic degradation of methyl orange (MO) under visible light irradiation. The results showed that the photocatalytic performance of the co-doped TiO2 was related with the hydrothermal temperature and the molar ratio of N/Ti, and they showed higher acitivites than pure TiO2. Results determined by fluorescence technique revealed that irradiation (lambda > 400 nm) of TiO2 photocatalyst dispersed in MO solution induces the generation of the highly active hydroxyl radicals (OH). It indicated the photocatalytic activities of TiO2 photocatalyst were correlation with the formation rate of hydroxyl radicals (OH) and other active oxygen species.

  8. Photoelectrocatalytic degradation of methylene blue using F doped TiO2 photoelectrode under visible light irradiation.

    PubMed

    Liu, Dong; Tian, Renwen; Wang, Jianqiao; Nie, Er; Piao, Xianqing; Li, Xin; Sun, Zhuo

    2017-10-01

    Photoelectrocatalysis (PEC) has attracted great interest due to cost effectiveness and high efficiency in water treatment. In this study, F doped TiO2 (F-TiO2) photoelectrodes with honeycomb like morphology were prepared, and the PEC performance was investigated. F-TiO2 particles that showed enhanced absorption of visible light were synthesized via a sol-gel method. F-TiO2 particles were anchored onto the surface of F-doped SnO2 glass by a screen-printing method to prepare the F-TiO2 photoelectrodes. The PEC performance of the F-TiO2 photoelectrodes was investigated via the degradation of methylene blue (MB) under visible light irradiation. The results show that the F-TiO2 photoelectrodes exhibited an excellent PEC performance that was affected by the F doping content, applied bias and solution pH. A maximum decolorization percentage of 97.8% was achieved by the FT-15 photoelectrode, with a 1.4 V bias at pH 9.94 after 4.0 h of visible light irradiation. The high PEC performance of the F-TiO2 photoelectrodes is mainly ascribed to the efficient separation of electron-hole (e(-)-h(+)) pairs and the creation of active radicals such as hydroxyl radicals (OH). The PEC decolorization kinetic data were analyzed using the first-order kinetic model and the Langmuir-Hinshelwood (L-H) model. The data indicates that the PEC degradation of MB molecules mainly occurred on the surface of the F-TiO2 photoelectrodes, and the MB molecules were discolored mainly by h(+) (41.5%) and OH (46.5%). In addition, 8.2% of the MB molecules were discolored by other oxidative species, and 3.8% of the MB molecules were discolored by self-sensitized oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Effect of Ga doping concentration on the luminescence efficiency of GaN light-emitting diodes with Ga-doped ZnO contacts

    NASA Astrophysics Data System (ADS)

    Kim, Chang Oh; Kim, Sung; Shin, Dong Hee; Shin, Dong Yeol; Choi, Suk-Ho; Hwang, Sung Won; Cha, Nam-Goo; Kang, Sammook

    2012-11-01

    P-n junction GaN light-emitting diodes (LEDs) were fabricated using Ga-doped ZnO (GZO) films as electrical contacts and characterized by electroluminescence (EL) and current-voltage (I-V) measurements. GaN p-n epilayers with a total thickness of ~6 μm were grown on c-plane (0001) sapphire substrates by metal-organic chemical vapor deposition. Half region of the p-GaN layer was etched until the n-GaN layer was exposed, and 100-nm-thick GZO contacts were deposited on the p- and n-GaN layers by RF sputtering with varying Ga concentration ( n G ) from 1 to 5 mol%. Based on the results of Hall effect, photoluminescence (PL), and X-ray diffraction (XRD), the GZO films were expected to act as best electrical contacts for the LEDs at n G = 2 mol%. Under forward-bias conditions, the I-V curves showed diode characteristics except n G = 5 mol%, and the leakage current was minimized at n G = 2 mol%. Two dominant EL peaks of ultraviolet and yellow emissions were observed at ~376 and ~560 nm, and attributed to near-band-edge- and defect-related radiative transitions, respectively. At n G = 2 mol%, the UV EL showed markedly large intensities for all injection currents, consistent with the results of Hall effect, PL, I-V, and XRD.

  10. Investigation and process optimization of SONOS cell's drain disturb in 2-transistor structure flash arrays

    NASA Astrophysics Data System (ADS)

    Xu, Zhaozhao; Qian, Wensheng; Chen, Hualun; Xiong, Wei; Hu, Jun; Liu, Donghua; Duan, Wenting; Kong, Weiran; Na, Wei; Zou, Shichang

    2017-03-01

    The mechanism and distribution of drain disturb (DD) are investigated in silicon-oxide-nitride-oxide-silicon (SONOS) flash cells. It is shown that DD is the only concern in this paper. First, the distribution of trapped charge in nitride layer is found to be non-localized (trapped in entire nitride layer along the channel) after programming. Likewise, the erase is also non-localized. Then, the main disturb mechanism: Fowler Nordheim tunneling (FNT) has been confirmed in this paper with negligible disturb effect from hot-hole injection (HHI). And then, distribution of DD is confirmed to be non-localized similarly, which denotes that DD exists in entire tunneling oxide (Oxide for short). Next, four process optimization ways are proposed for minimization of DD, and VTH shift is measured. It reveals that optimized lightly doped drain (LDD), halo, and channel implant are required for the fabrication of a robust SONOS cell. Finally, data retention and endurance of the optimized SONOS are demonstrated.

  11. Ag-doped ZnO nanorods coated metal wire meshes as hierarchical photocatalysts with high visible-light driven photoactivity and photostability.

    PubMed

    Hsu, Mu-Hsiang; Chang, Chi-Jung

    2014-08-15

    Ag-doped ZnO nanorods were grown on stainless-steel wire meshes to fabricate the hierarchical photocatalysts with excellent visible light driven activity and anti-photocorrosion property. Effects of Ag doping and the surface structure on the surface chemistry, surface wetting properties, absorption band shift, photoelectrochemical response, and photocatalytic decolorization properties of the hierarchical photocatalysts, together with the stability of photocatalytic activity for recycled photocatalysts were investigated. Ag doping leads to red-shift in the absorption band and increased visible light absorption. Nanorods coated wire meshes hierarchical structure not only increases the surface area of photocatalysts but also makes the surface hydrophilic. The photocatalytic activity enhancement and reduced photocorrosion can be achieved because of increased surface area, enhanced hydrophilicity, and the interaction between the metal wire/ZnO and Ag/ZnO heterostructure interface which can improve the charge separation of photogenerated charge carriers.

  12. Hydrothermal synthesis and visible-light-driven photocatalytic degradation for tetracycline of Mn-doped SrTiO3 nanocubes

    NASA Astrophysics Data System (ADS)

    Wu, Guoling; Li, Ping; Xu, Dongbo; Luo, Bifu; Hong, Yuanzhi; Shi, Weidong; Liu, Chunbo

    2015-04-01

    Visible-light-driven manganese doped SrTiO3 nanocubes with various manganese atomic percentages in the range of 3-7%, were prepared by a hydrothermal method. These obtained photocatalysts were systematically characterized by XRD, EDX, TEM, STEM, XPS, UV-vis, PL, EIS. The results demonstrated that the Mn4+ has substituted into the lattice of SrTiO3 nanocubes and the absorption onset shifted toward the visible region. It is beneficial to the photocatalytic degradation of tetracycline under the visible light irradiation. Interestingly, the optimal doping atomic percentages at 5% exhibited the highest degradation rates (66.7%) in 60 min. The high photocatalytic activity could be ascribed to the Mn doping adjustment the energy band of SrTiO3 and the highly effective separation of photo-generated electron-hole pairs. Furthermore, the possible photocatalytic mechanism has been discussed based on the active species trapping experiments and ESR analysis.

  13. Enhanced photocatalytic activity of S-doped TiO2-ZrO2 nanoparticles under visible-light irradiation.

    PubMed

    Tian, Guohui; Pan, Kai; Fu, Honggang; Jing, Liqiang; Zhou, Wei

    2009-07-30

    Porous nanocrystalline S-doped TiO2-ZrO2 visible-light photocatalysts were prepared through a one-step method. The resulting materials were characterized by X-ray diffraction (XRD), N(2) adsorption-desorption measurements, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS), Fourier transform infrared spectra (FT-IR) and electron paramagnetic resonance (ESR). It was found that modification by ZrO2 could effectively inhibit phase transformation, enhance visible-light absorption, and possess more surface hydroxyl groups. The photocatalytic activity of S-doped TiO2-ZrO2 was higher than that of unmodified S-doped TiO2 and Degussa P25. The enhanced photocatalytic activity could be attributed to the higher specific area, smaller crystal size, porous structure and more surface hydroxyl groups in the catalyst.

  14. Multicolor upconversion luminescence of rare-earth doped Y2CaZnO5 nanophosphors for white lighting-emitting diodes

    NASA Astrophysics Data System (ADS)

    Rajeswari, R.; Surendra Babu, S.; Jayasankar, C. K.

    2014-02-01

    Rare earth doped Y2CaZnO5 nanophosphors were synthesized via the citrate-gel combustion method. Transmission electron microscopy measurements reveal that the particles are distributed uniformly within the size range of 10-30 nm. The Er3+-doped Y2CaZnO5 nanophosphors show strong green upconversion luminescence, which is visible to the naked eye even at 20 mW excitation power of 980 nm diode laser. When these phosphors are codoped with Yb3+ ions, the emission changed to reddish color at higher Yb3+ ion concentrations. Moreover, these phosphors emitted bright white light luminescence when it is triply doped with Er3+/Tm 3+/Yb3+ ions, indicates Y2CaZnO5 nanophosphors are an ideal candidate for phosphor converted white light emitting diodes.

  15. GaAs MESFET with lateral non-uniform doping

    NASA Technical Reports Server (NTRS)

    Wang, Y. C.; Bahrami, M.

    1983-01-01

    An analytical model of the GaAs MESFET with arbitrary non-uniform doping is presented. Numerical results for linear lateral doping profile are given as a special case. Theoretical considerations predict that better device linearity and improved F(T) can be obtained by using linear lateral doping when doping density increases from source to drain.

  16. Iron-Doped Carbon Nitride-Type Polymers as Homogeneous Organocatalysts for Visible Light-Driven Hydrogen Evolution.

    PubMed

    Gao, Lin-Feng; Wen, Ting; Xu, Jing-Yin; Zhai, Xin-Ping; Zhao, Min; Hu, Guo-Wen; Chen, Peng; Wang, Qiang; Zhang, Hao-Li

    2016-01-13

    Graphitic carbon nitrides have appeared as a new type of photocatalyst for water splitting, but their broader and more practical applications are oftentimes hindered by the insolubility or difficult dispersion of the material in solvents. We herein prepared novel two-dimensional (2D) carbon nitride-type polymers doped by iron under a mild one-pot method through preorganizing formamide and citric acid precursors into supramolecular structures, which eventually polycondensed into a homogeneous organocatalyst for highly efficient visible light-driven hydrogen evolution with a rate of ∼16.2 mmol g(-1) h(-1) and a quantum efficiency of 0.8%. Laser photolysis and electrochemical impedance spectroscopic measurements suggested that iron-doping enabled strong electron coupling between the metal and the carbon nitride and formed unique electronic structures favoring electron mobilization along the 2D nanomaterial plane, which might facilitate the electron transfer process in the photocatalytic system and lead to efficient H2 evolution. In combination with electrochemical measurements, the electron transfer dynamics during water reduction were depicted, and the earth-abundant Fe-based catalyst may open a sustainable strategy for conversion of sunlight into hydrogen energy and cope with current challenging energy issues worldwide.

  17. Transparent indium oxide films doped with high Lewis acid strength Ge dopant for phosphorescent organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kang, Sin-Bi; Lim, Jong-Wook; Lee, Sunghun; Kim, Jang-Joo; Kim, Han-Ki

    2012-08-01

    We report on Ge-doped In2O3(IGO) films prepared by co-sputtering GeO2 and In2O3 targets for anode of phosphorescent organic light-emitting diodes (POLEDs). Under optimized annealing conditions, the IGO film exhibited a low sheet resistance of 14.0 Ω/square, a high optical transmittance of 86.9% and a work function of 5.2 eV, comparable to conventional Sn-doped In2O3 (ITO) films. Due to the higher Lewis acid strength of the Ge4+ ion (3.06) than that of Sn3+(1.62), the IGO film showed higher transparency in the near infrared and higher carrier mobility of 39.16 cm2 V-1 s-1 than the ITO films. In addition, the strongly preferred (2 2 2) orientation of the IGO grains, caused by Zone II grain growth during rapid thermal annealing, increased the carrier mobility and improved the surface morphology of the IGO film. POLEDs fabricated on IGO anodes showed identical current density-voltage-luminance curves and efficiencies to POLEDs with ITO electrodes due to the low sheet resistance and high transmittance of the IGO anode.

  18. Rare-earth ions doped heavy metal germanium tellurite glasses for fiber lighting in minimally invasive surgery.

    PubMed

    Yang, D L; Gong, H; Pun, E Y B; Zhao, X; Lin, H

    2010-08-30

    In Er(3+)/Yb(3+) codoped Na(2)O-ZnO-PbO-GeO(2)-TeO(2) (NZPGT) glass fiber, a clear and compact green upconversion amplified spontaneous emission (ASE) trace is observed, and the NZPGT glasses are proved to be a desirable candidate in fabricating low-phonon energy fiber. Intense green upconversion luminescence of Er(3+), balanced green and red upconversion emissions of Ho(3+), and dominant three-photon blue upconversion fluorescence of Tm(3+) have been represented. By varying the excitation power of 974 nm wavelength laser diode, a series of green and white fluorescences have been achieved in Tm(3+)/Er(3+)/Yb(3+) and Tm(3+)/Ho(3+)/Yb(3+) triply doped glass systems, respectively. These results reveal that high-intensity blue, green, and white upconversion ASE fluorescences, which can be adopted for lighting in minimally invasive photodynamic therapy and minimally invasive surgery, are reasonable to be expected in rare-earth doped NZPGT glass fibers.

  19. Highly efficient non-doped orange-red phosphorescent organic light-emitting devices based on a novel iridium complex

    NASA Astrophysics Data System (ADS)

    Qi, Yige; Wang, Xu; Li, Ming; Yu, Junsheng; Lu, Zhiyun

    2014-09-01

    The non-doped orange-red phosphorescent organic light-emitting device (PHOLED) based on a newly synthesized iridium complex, bis[2-(biphenyl-4-yl)benzothiazole-N,C2']iridium(III)(acetylacetonate) [(4Phbt)2Ir(acac)] has been demonstrated. The non-doped device with (4Phbt)2Ir(acac) as the emissive layer achieved ideal turn-on voltage (<4 V) and superior power efficiency (5 lm/W) as well as luminance efficiency (6 cd/A), respectively. Our device performance indicates that (4Phbt)2Ir(acac) possesses excellent self-quenching-resistant property. The potential of this property is originated from the introduction of bulky and twisted aromatic substituents in ligands, which break the molecular planarity and obstruct the molecular packing. Besides, the high electroluminescence efficiency is also attributed to that the energy level alignment between (4Phbt)2Ir(acac) and adjacent charge-transporting materials forms a well-like structure, which confines exciton effectively in emissive layer.

  20. Structure, morphology and optical characterization of Dy3+-doped BaYF5 nanocrystals for warm white light emitting devices

    NASA Astrophysics Data System (ADS)

    Haritha, P.; Martín, I. R.; Dwaraka Viswanath, C. S.; Vijaya, N.; Venkata Krishnaiah, K.; Jayasankar, C. K.; Haranath, D.; Lavín, V.; Venkatramu, V.

    2017-08-01

    The barium yttrium fluoride BaYF5 nanocrystalline powders doped with different concentrations of Dy3+ ions have been synthesized via a hydrothermal method and studied their structural, morphological, thermal, vibrational, and optical properties. These nanopowders have been crystallized in a single phase of the tetragonal structure with the average size of around 30 nm having spherical shape in morphology. Upon excitations at 350 and 387 nm, Dy3+ -doped BaYF5 nanocrystals exhibit strong blue and yellow emissions ascribed to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions, respectively. Decay curves of the 4F9/2 level of Dy3+ ion in BaYF5 nanocrystals exhibit non-exponential nature due to the dipole-dipole interaction between Dy3+ ions, confirmed by Inokuti-Hirayama model. The quantum yield for these nanocrystals have been found to be increased from 4.64% to 11.61% as the concentration of Dy3+ ions increases from 1.0 mol% to 2.0 mol% and then decreased to 10.68% as the dopant concentration increased to 5.0 mol%. Moreover, color coordinates and correlated color temperatures have been evaluated as a function of concentration and excitation wavelength and found to be in the warm white light region for all Dy3+ concentrations.

  1. Observation of intermediate bands in Eu3+ doped YPO4 host: Li+ ion effect and blue to pink light emitter

    NASA Astrophysics Data System (ADS)

    Parchur, Abdul Kareem; Prasad, Amresh Ishawar; Rai, Shyam Bahadur; Tewari, Raghvendra; Sahu, Ranjan Kumar; Okram, Gunadhor Singh; Singh, Ram Asaray; Ningthoujam, Raghumani Singh

    2012-09-01

    This article explores the tuning of blue to pink colour generation from Li+ ion co-doped YPO4:5Eu nanoparticles prepared by polyol method at ˜100-120 °C with ethylene glycol (EG) as a capping agent. Interaction of EG molecules capped on the surface of the nanoparticles and/or created oxygen vacancies induces formation of intermediate/mid gap bands in the host structure, which is supported by UV-Visible absorption data. Strong blue and pink colors can be observed in the cases of as-prepared and 500 °C annealed samples, respectively. Co-doping of Li+ enhances the emission intensities of intermediate band as well as Eu3+. On annealing as-prepared sample to 500 °C, the intermediate band emission intensity decreases, whereas Eu3+ emission intensity increases suggesting increase of extent of energy transfer from the intermediate band to Eu3+ on annealing. Emission intensity ratio of electric to magnetic dipole transitions of Eu3+ can be varied by changing excitation wavelength. The X-ray photoelectron spectroscopy (XPS) study of as-prepared samples confirms the presence of oxygen vacancies and Eu3+ but absence of Eu2+. Dispersed particles in ethanol and polymer film show the strong blue color, suggesting that these materials will be useful as probes in life science and also in light emitting device applications.

  2. 21 CFR 884.3200 - Cervical drain.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cervical drain. 884.3200 Section 884.3200 Food and... OBSTETRICAL AND GYNECOLOGICAL DEVICES Obstetrical and Gynecological Prosthetic Devices § 884.3200 Cervical drain. (a) Identification. A cervical drain is a device designed to provide an exit channel for draining...

  3. 21 CFR 884.3200 - Cervical drain.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Cervical drain. 884.3200 Section 884.3200 Food and... OBSTETRICAL AND GYNECOLOGICAL DEVICES Obstetrical and Gynecological Prosthetic Devices § 884.3200 Cervical drain. (a) Identification. A cervical drain is a device designed to provide an exit channel for draining...

  4. 21 CFR 884.3200 - Cervical drain.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Cervical drain. 884.3200 Section 884.3200 Food and... OBSTETRICAL AND GYNECOLOGICAL DEVICES Obstetrical and Gynecological Prosthetic Devices § 884.3200 Cervical drain. (a) Identification. A cervical drain is a device designed to provide an exit channel for draining...

  5. 21 CFR 884.3200 - Cervical drain.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Cervical drain. 884.3200 Section 884.3200 Food and... OBSTETRICAL AND GYNECOLOGICAL DEVICES Obstetrical and Gynecological Prosthetic Devices § 884.3200 Cervical drain. (a) Identification. A cervical drain is a device designed to provide an exit channel for draining...

  6. 21 CFR 884.3200 - Cervical drain.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cervical drain. 884.3200 Section 884.3200 Food and... OBSTETRICAL AND GYNECOLOGICAL DEVICES Obstetrical and Gynecological Prosthetic Devices § 884.3200 Cervical drain. (a) Identification. A cervical drain is a device designed to provide an exit channel for draining...

  7. Enhanced visible light photocatalytic hydrogen evolution of sulfur-doped polymeric g-C{sub 3}N{sub 4} photocatalysts

    SciTech Connect

    Ge, Lei; Han, Changcun; Xiao, Xinlai; Guo, Lele; Li, Yujing

    2013-10-15

    Graphical abstract: - Highlights: • Sulfur-doped g-C{sub 3}N{sub 4} was prepared using thiourea as sulfur source. • The sulfur-doped g-C{sub 3}N{sub 4} shows significantly enhanced H{sub 2} evolution activity. • The doped sulfur species plays key roles in the improvement of H{sub 2} production. • Photocatalytic mechanism is proposed based on the experimental results. • The mechanism is confirmed by PL spectra and transient photocurrent curves. - Abstract: Visible light-activated sulfur-doped g-C{sub 3}N{sub 4} photocatalysts were successfully synthesized using thiourea as sulfur source. The obtained photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microcopy, ultraviolet–visible diffuse reflection spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy and transient photocurrent response. The sulfur-doped g-C{sub 3}N{sub 4} photocatalysts show beneficial effects on visible light absorption, electron–hole pair generation and separation. The sulfur species doped in the samples was identified as S{sup 2−} to replace N atoms in the g-C{sub 3}N{sub 4} framework. The photocatalytic activities of the sulfur-doped g-C{sub 3}N{sub 4} under visible light were evaluated by hydrogen evolution from water splitting in aqueous solution containing methanol. The sulfur-doped g-C{sub 3}N{sub 4} photocatalyst showed the highest photocatalytic performance with H{sub 2} evolution rate of 12.16 μmol h{sup −1}, about 6 times higher than un-doped g-C{sub 3}N{sub 4}. It can be concluded that the sulfur species play a vital role and act as active sites in the photocatalytic reaction. This novel sulfur-doped g-C{sub 3}N{sub 4} can be potentially used in energy and environmental applications.

  8. History Dependent Magnetoresistance in Lightly Doped LaZxSrxCuO4Thin Films

    SciTech Connect

    Bozovic I.; Shi, X.; Popovic, D.; Panagopoulos, C.; Logvenov, G.; Bollinger, A.T.

    2012-06-01

    The in-plane magnetoresistance (MR) in atomically smooth La{sub 2-x}Sr{sub x}CuO{sub 4} thin films grown by molecular-beam-epitaxy was measured in magnetic fields B up to 9 T over a wide range of temperatures T. The films, with x = 0.03 and x = 0.05, are insulating, and the positive MR emerges at T < 4 K. The positive MR exhibits glassy features, including history dependence and memory, for all orientations of B. The results show that this behavior, which reflects the onset of glassiness in the dynamics of doped holes, is a robust feature of the insulating state.

  9. Visible light activated photocatalytic degradation of tetracycline by a magnetically separable composite photocatalyst: Graphene oxide/magnetite/cerium-doped titania.

    PubMed

    Cao, Muhan; Wang, Peifang; Ao, Yanhui; Wang, Chao; Hou, Jun; Qian, Jin

    2016-04-01

    In this study, magnetic graphene oxide-loaded Ce-doped titania (MGO-Ce-TiO2) hybridized composite was prepared by a facile method. The as-prepared samples exhibited good adsorption capacity, high visible-light photoactive and magnetic separability as a novel photocatalyst in the degradation of tetracyclines (TC). The intermediate products and photocatalytic route of TC were proposed based on the analysis results of LC-MS. Moreover, the repeatability of the photoactivity with the use of MGO-Ce-TiO2 was investigated in the multi-round experiments with the assistance of an applied magnetic field. Therefore, the prepared composite photocatalysts were considered as a kind of promising photocatalyst in a suspension reaction system, in which they can offer effectively recovery ability. The effect of MGO content on the photocatalytic performance was also studied, and an optimum content was obtained. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Photocatalytic degradation of BTEX using W-doped TiO2 immobilized on fiberglass cloth under visible light

    NASA Astrophysics Data System (ADS)

    Sangkhun, Weradeach; Laokiat, Laksana; Tanboonchuy, Visanu; Khamdahsag, Pummarin; Grisdanurak, Nurak

    2012-10-01

    W-doped TiO2 were immobilized on fiberglass cloth (FGC). The catalyst possessed small crystallite sizes with a red-shift on an absorption edge. Good dispersion was observed over the immobilized catalyst. The photocatalytic degradation of gaseous BTEX was conducted in a flow reactor under day-light fluorescent. Parameters including gas flowrate, catalyst loading, initial concentration and relative humidity (%RH) were investigated. The prepared catalysts showed higher efficiency than that of TiO2 approximately 18, 3, 3 and 2.5× for benzene, toluene, ethylbenzene and o-xylene, respectively. The condition to achieve 100% BTEX removal was found at 20 min/ml, catalyst loading 0.1 mg/cm2 and 30% RH.

  11. Study of electrical current reconstruction on macropore arrays etched electrochemically on lightly-doped n-Si

    NASA Astrophysics Data System (ADS)

    Zhan, Chang-Yong; Zou, Yu; Jiang, Wen; Fan, Xiao-Qiang; Jiang, Yong; Feng, Qi-Jie; Li, Xing-Liang; Sun, Hua; Wu, Jian-Chun

    2016-01-01

    Silicon macropore arrays are fabricated on lightly-doped n-Si by electrochemical etching. The opening diameter, inner diameter, and wall thickness of the macropores are observed to depend on HF concentration and current. A current reconstruction model is proposed to elucidate the formation mechanism of the macropores. Two geometric models are established for the silicon macropores according to the experimental results. The finite element method is used to simulate the electric field and current in the electrolyte-silicon system. The reconstruction of electrical current on the silicon macropore arrays is described by simulating the electric field and current. The ratio of major to minor semi-axes of the elliptical pore (b/a) decreases with increasing the ratio of diameter to wall thickness as confirmed experimentally. The results indicate that the b/a ratio is correlated with the HF concentration and applied voltage.

  12. Low Temperature Specific Heat in Lightly Mn-Substituted Electron-Doped SrTiO3

    NASA Astrophysics Data System (ADS)

    Okuda, Tetsuji; Hata, Hiroto; Eto, Takahiro; Sobaru, Shogo; Oda, Ryosuke; Noda, Masaaki; Kuwahara, Hideki

    2017-08-01

    We found large changes in the low-temperature specific heat (low-T C) in the lightly Mn-substituted electron-doped perovskites Sr0.95La0.05Ti1-yMnzO3 with y = 0.02 and 0.04 by applying magnetic fields up to 9 T. The changes in the low-T C are qualitatively well explained by the Schottky specific heat (CSch) of localized spins of the Mn 3d electrons in weak internal magnetic fields via itinerant electrons. However, the actual numbers of localized spins estimated from CSch are about 30% smaller than the expected values. Part of the localized spins of the Mn 3d electrons may disappear due to Kondo coupling with the itinerant electrons.

  13. Novel rare earth ions-doped oxyfluoride nano-composite with efficient upconversion white-light emission

    SciTech Connect

    Chen Daqin; Wang Yuansheng Yu Yunlong; Huang Ping; Weng Fangyi

    2008-10-15

    Transparent SiO{sub 2}-Al{sub 2}O{sub 3}-NaF-YF{sub 3} bulk nano-composites triply doped with Ho{sup 3+}, Tm{sup 3+} and Yb{sup 3+} were fabricated by melt-quenching and subsequent heating. X-ray diffraction and transmission electron microscopy measurements demonstrated the homogeneous precipitation of the {beta}-YF{sub 3} crystals with mean size of 20 nm among the glass matrix, and rare earth ions were found to partition into these nano-crystals. Under single 976 nm laser excitation, intense red, green and blue upconversion emissions were simultaneously observed owing to the successive energy transfer from Yb{sup 3+} to Ho{sup 3+} or Tm{sup 3+}. Various colors of luminescence, including bright perfect white light, can be easily tuned by adjusting the concentrations of the rare earth ions in the material. The overall energy efficiency of the white-light upconversion was estimated to be about 0.2%. - Graphical abstract: Under single 976 nm laser excitation, intense red, green and blue upconversion emissions were simultaneously observed owing to the successive energy transfer from Yb{sup 3+} to Ho{sup 3+} or Tm{sup 3+}. Various colors of luminescence, including bright perfect white light with CIE-X=0.351 and CIE-Y=0.306, can be easily tuned by adjusting the concentrations of the rare earth ions in the transparent oxyfluoride glass ceramics.

  14. Highly Visible Light Activity of Nitrogen Doped TiO2 Prepared by Sol-Gel Approach

    NASA Astrophysics Data System (ADS)

    Than, Le Dien; Luong, Ngo Sy; Ngo, Vu Dinh; Tien, Nguyen Manh; Dung, Ta Ngoc; Nghia, Nguyen Manh; Loc, Nguyen Thai; Thu, Vu Thi; Lam, Tran Dai

    2017-01-01

    A simple approach was explored to prepare N-doped anatase TiO2 nanoparticles (N-TiO2 NPs) from titanium chloride (TiCl4) and ammonia (NH3) via sol-gel method. The effects of important process parameters such as calcination temperatures, NH3/TiCl4 molar ratio ( R N) on crystallite size, structure, phase transformation, and photocatalytic activity of titanium dioxide (TiO2) were thoroughly investigated. The as-prepared samples were characterized by ultraviolet-visible spectroscopy, x-ray diffraction, transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. The photocatalytic activity of the samples was evaluated upon the degradation of methylene blue aqueous solution under visible-light irradiation. The results demonstrated that both calcination temperatures and NH3/TiCl4 molar ratios had significant impacts on the formation of crystallite nanostructures, physicochemical, as well as catalytic properties of the obtained TiO2. Under the studied conditions, calcination temperature of 600°C and NH3/TiCl4 molar ratio of 4.2 produced N-TiO2 with the best crystallinity and photocatalytic activity. The high visible light activity of the N-TiO2 nanomaterials was ascribed to the interstitial nitrogen atoms within TiO2 lattice units. These findings could provide a practical pathway capable of large-scale production of a visible light-active N-TiO2 photocatalyst.

  15. Biogenic C-doped titania templated by cyanobacteria for visible-light photocatalytic degradation of Rhodamine B.

    PubMed

    He, Jiao; Zi, Guoli; Yan, Zhiying; Li, Yongli; Xie, Jiao; Duan, Deliang; Chen, Yongjuan; Wang, Jiaqiang

    2014-05-01

    Cyanobacteria, which occurred in eutrophic water harvest solar light to carry out photosynthesis with high efficiency. In this work, cyanobacteria (Microcystis sp.) were used as biotemplate to synthesize titania structure. The synthesized titania sample had similar morphology to that of the original template in spite of the fragile unicellular structures and extremely high water content of cyanobacterial cells. Incorporation of biogenic C, as well as the morphology inherited from biotemplate improved visible-light absorbance of the titania structure. The sample exhibited higher visible-light photocatalytic activity than commercial titania photocatalyst Degussa P25 for Rhodamine B (RhB) degradation. Compared with those C-doped titania photocatalysts prepared by other methods, cyanobacteria templated titania photocatalyst offer some potential for competitive advantages. The reported strategy opened up a new use for the cyanobacteria. It could also be used for titania in applications such as treatment of polluted water, dye-sensitized solar cells, or other regions. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

  16. Li and Ag Co-Doped ZnO Photocatalyst for Degradation of RO 4 Dye Under Solar Light Irradiation.

    PubMed

    Dhatshanamurthi, P; Shanthi, M

    2016-06-01

    The synthesis of Li doped Ag-ZnO (Li-Ag-ZnO) has been successfully achieved by a sonochemically assisted precipitation-decomposition method. The synthesized catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL), X-ray photoelectron spectra (XPS) and BET surface area measurements. The photocatalytic activity of Li-Ag-ZnO was investigated for the degradation of Reactive orange 4 (RO 4) dye in aqueous solution under solar light irradiation. Co-dopants shift the absorbance of ZnO to the visible region. Li-Ag-ZnO is found to be more efficient than Ag-ZnO, Li-ZnO, commercial ZnO and prepared ZnO at pH 7 for the mineralization of RO 4 dye under solar light irradiation. The influences of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo-mineralization of RO 4 have been analyzed. The mineralization of RO 4 dye has been confirmed by COD measurements. A degradation mechanism is proposed for the degradation of RO 4 under solar light. The catalyst was found to be more stable and reusable.

  17. Visible light activity of Ag-loaded and guanidine nitrate-doped nano-TiO2: Degradation of dichlorophenol and antibacterial properties

    EPA Science Inventory

    To utilize visible light, co-doped nano-TiO2 was prepared via “one pot” synthesis using mild reaction conditions and benign precursors. Synthesis was optimized using an appropriate experimental design taking into account silver content and calcination temperature. The optimized ...

  18. N Doping to ZnO Nanorods for Photoelectrochemical Water Splitting under Visible Light: Engineered Impurity Distribution and Terraced Band Structure

    PubMed Central

    Wang, Meng; Ren, Feng; Zhou, Jigang; Cai, Guangxu; Cai, Li; Hu, Yongfeng; Wang, Dongniu; Liu, Yichao; Guo, Liejin; Shen, Shaohua

    2015-01-01

    Solution-based ZnO nanorod arrays (NRAs) were modified with controlled N doping by an advanced ion implantation method, and were subsequently utilized as photoanodes for photoelectrochemical (PEC) water splitting under visible light irradiation. A gradient distribution of N dopants along the vertical direction of ZnO nanorods was realized. N doped ZnO NRAs displayed a markedly enhanced visible-light-driven PEC photocurrent density of ~160 μA/cm2 at 1.1 V vs. saturated calomel electrode (SCE), which was about 2 orders of magnitude higher than pristine ZnO NRAs. The gradiently distributed N dopants not only extended the optical absorption edges to visible light region, but also introduced terraced band structure. As a consequence, N gradient-doped ZnO NRAs can not only utilize the visible light irradiation but also efficiently drive photo-induced electron and hole transfer via the terraced band structure. The superior potential of ion implantation technique for creating gradient dopants distribution in host semiconductors will provide novel insights into doped photoelectrode materials for solar water splitting. PMID:26262752

  19. Visible light activity of Ag-loaded and guanidine nitrate-doped nano-TiO2: Degradation of dichlorophenol and antibacterial properties

    EPA Science Inventory

    To utilize visible light, co-doped nano-TiO2 was prepared via “one pot” synthesis using mild reaction conditions and benign precursors. Synthesis was optimized using an appropriate experimental design taking into account silver content and calcination temperature. The optimized ...

  20. N Doping to ZnO Nanorods for Photoelectrochemical Water Splitting under Visible Light: Engineered Impurity Distribution and Terraced Band Structure

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Ren, Feng; Zhou, Jigang; Cai, Guangxu; Cai, Li; Hu, Yongfeng; Wang, Dongniu; Liu, Yichao; Guo, Liejin; Shen, Shaohua

    2015-08-01

    Solution-based ZnO nanorod arrays (NRAs) were modified with controlled N doping by an advanced ion implantation method, and were subsequently utilized as photoanodes for photoelectrochemical (PEC) water splitting under visible light irradiation. A gradient distribution of N dopants along the vertical direction of ZnO nanorods was realized. N doped ZnO NRAs displayed a markedly enhanced visible-light-driven PEC photocurrent density of ~160 μA/cm2 at 1.1 V vs. saturated calomel electrode (SCE), which was about 2 orders of magnitude higher than pristine ZnO NRAs. The gradiently distributed N dopants not only extended the optical absorption edges to visible light region, but also introduced terraced band structure. As a consequence, N gradient-doped ZnO NRAs can not only utilize the visible light irradiation but also efficiently drive photo-induced electron and hole transfer via the terraced band structure. The superior potential of ion implantation technique for creating gradient dopants distribution in host semiconductors will provide novel insights into doped photoelectrode materials for solar water splitting.

  1. Self-doped Ti(3+)-TiO2 as a photocatalyst for the reduction of CO2 into a hydrocarbon fuel under visible light irradiation.

    PubMed

    Sasan, Koroush; Zuo, Fan; Wang, Yuan; Feng, Pingyun

    2015-08-28

    Self-doped TiO2 shows visible light photocatalytic activity, while commercial TiO2 (P25) is only UV responsive. The incorporation of Ti(3+) into TiO2 structures narrows the band gap (2.90 eV), leading to significantly increased photocatalytic activity for the reduction of CO2 into a renewable hydrocarbon fuel (CH4) in the presence of water vapour under visible light irradiation.

  2. Spin-dependent photophysics in polymers lightly doped with fullerene derivatives: Photoluminescence and electrically detected magnetic resonance

    NASA Astrophysics Data System (ADS)

    Zerai Tedlla, B.; Zhu, F.; Cox, M.; Koopmans, B.; Goovaerts, E.

    2015-02-01

    Lightly fullerene-doped polymers are suitable composite systems to study spin-dependent bimolecular interactions among charge excitations due to their long lifetimes in these systems. These interactions can affect the photocurrent as well as the open-circuit voltage in an organic solar cell. Combining photoluminescence detected magnetic resonance (PLDMR) and electrically detected magnetic resonance (EDMR) spectroscopies we study films and devices of poly(p -phenylene vinylene) polymers poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) and superyellow PPV (SY-PPV) lightly doped with various fullerene derivatives [6,6]-phenyl C61 butyric acid methyl ester (PCBM), bis[60]PCBM (bis-PCBM), indene-C60 bisadduct (ICBA), and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM). (i) We demonstrate strong fullerene triplet exciton (TE) production in SY-PPV:fullerene blends, whereas this is absent in MDMO-PPV:PCBM and only very weak in MDMO-PPV:ICBA. The low TE production in blends with MDMO-PPV is attributed to a weaker singlet-singlet energy-transfer coupling and an unfavorable triplet level alignment between the blend components. (ii) The fullerene TE spectra are analyzed on the basis of a single type of triplet excitation in PCBM, bis-PCBM, and ICBA, and two triplet species in PC70BM which are attributed to the α- and β-type isomers of the latter molecule. (iii) The sign change with increasing temperature of the g ˜2 sharp central line in photo-EDMR, which is observed both in pristine SY-PPV and in blends with fullerene, is correlated to a transition from dominant TE-polaron annihilation to nongeminate polaron recombination processes.

  3. Photocatalytic comparison of Cu- and Ag-doped TiO2/GF for bioaerosol disinfection under visible light

    NASA Astrophysics Data System (ADS)

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2015-12-01

    Photocatalysts, TiO2/glass fiber (TiO2/GF), Cu-doped TiO2/glass fiber (Cu-TiO2/GF) and Ag-doped TiO2/glass fiber (Ag-TiO2/GF), were synthesized by a sol-gel method. They were then used to disinfect Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in bioaerosols under visible light irradiation. TiO2/GF did not show any significant disinfection effect. Both Cu and Ag acted as intermediate agents to enhance separation efficiency of electron-hole pairs of TiO2, leading to improved photocatalytic activity of Cu-TiO2/GF and Ag-TiO2/GF under visible light. Cu in Cu-TiO2/GF acted as a defective agent, increasing the internal quantum efficiency of TiO2, while Ag in Ag-TiO2/GF acted as a sensitive agent, enhancing the transfer efficiency of the electrons generated. The highest disinfection efficiencies of E. coli and S. aureus by Cu-TiO2/GF were 84.85% and 65.21%, respectively. The highest disinfection efficiencies of E. coli and S. aureus by Ag-TiO2/GF were 94.46% and 73.12%, respectively. Among three humidity conditions - 40±5% (dry), 60±5% (moderate), and 80±5% (humid) - the moderate humidity condition showed the highest disinfection efficiency for both E. coli and S. aureus. This study also showed that a Gram-negative bacterium (E. coli) were more readily disinfected by the photocatalysts than a Gram-positive bacterium (S. aureus).

  4. UV light photocatalytic degradation of organic dyes with Fe-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Saleh, Rosari; Djaja, Nadia Febiana

    2014-10-01

    Iron doped wurtzite ZnO nanoparticles were synthesized and characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, electron spin resonance and vibrating sample magnetometer techniques. The photocatalytic activities were also evaluated for the degradation of methyl orange and methylene blue under UV irradiation. The effects of various parameters, such as pH, dopant concentrations and photocatalytic dosage, were studied. The ESR results indicate the presence of Fe in both the Fe2+ and Fe3+ valence states. As the dopant concentrations increased, the number of spins due to Fe2+ ions increased and the number of spins due to Fe3+ ions decreased resulting in an increase in magnetization. The catalysts with the highest number of spins due to Fe2+ ions exhibited the optimum photocatalytic activity for the degradation of methyl orange and methylene blue. In addition, the role of photoactive species was investigated using a radical scavenger technique. The results indicated that the doping concentration is the most important factor in photocatalytic performance.

  5. Effect of nitrogen doping on the structural, optical and electrical properties of indium tin oxide films prepared by magnetron sputtering for gallium nitride light emitting diodes

    NASA Astrophysics Data System (ADS)

    Tian, Lifei; Cheng, Guoan; Wang, Hougong; Wu, Yulong; Zheng, Ruiting; Ding, Peijun

    2017-01-01

    The indium tin oxide (ITO) films are prepared by the direct current magnetron sputtering technology with an ITO target in a mixture of argon and nitrogen gas at room temperature. The blue transmittance at 455 nm rises from 63% to 83% after nitrogen doping. The resistivity of the ITO film reduces from 4.6 × 10-3 (undoped film) to 5.7 × 10-4 Ω cm (N-doped film). The X-ray photoelectron spectroscopy data imply that the binding energy of the In3d5/2 peak is declined 0.05 eV after nitrogen doping. The high resolution transmission electron microscope images show that the nitrogen loss density of the GaN/ITO interface with N-doped ITO film is smaller than that of the GaN/ITO interface with undoped ITO film. The forward turn-on voltage of gallium nitride light emitting diode reduces by 0.5 V after nitrogen doping. The fabrication of the N-doped ITO film is conducive to modify the N component of the interface between GaN and ITO layer.

  6. Effect of bismuth doping on the ZnO nanocomposite material and study of its photocatalytic activity under UV-light

    SciTech Connect

    Chandraboss, V.L.; Natanapatham, L.; Karthikeyan, B.; Kamalakkannan, J.; Prabha, S.; Senthilvelan, S.

    2013-10-15

    Graphical abstract: The hetero-junctions that are formed between the ZnO and the Bi provide an internal electric field that facilitates separation of the electron-hole pairs and induces faster carrier migration. Thus they often enhanced photocatalytic reaction. - Highlights: • Bi-doped ZnO nanocomposite material was prepared by precipitation method. • Characterized by XRD, HR-SEM with EDX, UV–visible DRS and FT-RAMAN analysis. • Bi-doped ZnO nanocomposite material was used to photodegradation of Congo red. • Mechanism and photocatalytic effect of nanocomposite material have been discussed. - Abstract: Bismuth (Bi)-doped ZnO nanocomposite material was prepared by precipitation method with doping precursors of bismuth nitrate pentahydrate and oxalic acid, characterized by X-ray diffraction (XRD), High Resolution-Scanning Electron Microscopy (HR-SEM) with Energy Dispersive X-ray (EDX) analysis, UV–visible Diffuse Reflectance Spectroscopy (UV–visible DRS) and Fourier Transform-Raman (FT-RAMAN) analysis. The enhanced photocatalytic activity of the Bi-doped ZnO is demonstrated through photodegradation of Congo red under UV-light irradiation. The mechanism of photocatalytic effect of Bi-doped ZnO nanocomposite material has been discussed.

  7. Enhanced photocatalytic degradation of dye under visible light on mesoporous microspheres by defects in manganese- and nitrogen-co-doped TiO2

    NASA Astrophysics Data System (ADS)

    Feng, Lu; Jiang, Heng; Zou, Mingming; Xiong, Fengqiang; Ganeshraja, Ayyakannu Sundaram; Pervaiz, Erum; Liu, Yinan; Zou, Shunying; Yang, Minghui

    2016-09-01

    Manganese- and nitrogen-co-doped mesoporous TiO2 microsphere photocatalysts are prepared by a simple sol-gel method with controllable sizes in the range of 400-500 nm and high surface area of 112 m2 g-1. Manganous acetate is the Mn source, and ammonia gas is the nitrogen source used. The dopants are found to be uniformly distributed in the TiO2 matrix. Interestingly, in (Mn,N)-co-doped TiO2, we observe an effective indirect band gap of 2.58 eV. (Mn,N)-co-doped mesoporous TiO2 microspheres show higher photocatalytic activity than Mn-TiO2 microspheres under visible light irradiation. Among the samples reported in this work, 0.2 at.% Mn doping and 500 °C 2-h nitriding condition give the highest photocatalytic activity. The observed photocatalytic activity in the (Mn,N)-co-doped TiO2 is attributed to the contribution from improved absorption due to trap levels of Mn, oxygen vacancies and N doping.

  8. Tuning near-gap electronic structure, interface charge transfer and visible light response of hybrid doped graphene and Ag3PO4 composite: Dopant effects

    PubMed Central

    He, Chao-Ni; Huang, Wei-Qing; Xu, Liang; Yang, Yin-Cai; Zhou, Bing-Xin; Huang, Gui-Fang; Peng, P.; Liu, Wu-Ming

    2016-01-01

    The enhanced photocatalytic performance of doped graphene (GR)/semiconductor nanocomposites have recently been widely observed, but an understanding of the underlying mechanisms behind it is still out of reach. As a model system to study the dopant effects, we investigate the electronic structures and optical properties of doped GR/Ag3PO4 nanocomposites using the first-principles calculations, demonstrating that the band gap, near-gap electronic structure and interface charge transfer of the doped GR/Ag3PO4(100) composite can be tuned by the dopants. Interestingly, the doping atom and C atoms bonded to dopant become active sites for photocatalysis because they are positively or negatively charged due to the charge redistribution caused by interaction. The dopants can enhance the visible light absorption and photoinduced electron transfer. We propose that the N atom may be one of the most appropriate dopants for the GR/Ag3PO4 photocatalyst. This work can rationalize the available experimental results about N-doped GR-semiconductor composites, and enriches our understanding on the dopant effects in the doped GR-based composites for developing high-performance photocatalysts. PMID:26923338

  9. Improvement of carrier injection symmetry and quantum efficiency in InGaN light-emitting diodes with Mg delta-doped barriers

    SciTech Connect

    Zhang, F.; Can, N.; Hafiz, S.; Monavarian, M.; Das, S.; Avrutin, V.; Özgür, Ü. Morkoç, H.

    2015-05-04

    The effect of δ-doping of In{sub 0.06}Ga{sub 0.94}N barriers with Mg on the quantum efficiency of blue light-emitting-diodes (LEDs) with active regions composed of 6 (hex) 3-nm In{sub 0.15}Ga{sub 0.85}N is investigated. Compared to the reference sample, δ-doping of the first barrier on the n-side of the LED structure improves the peak external quantum efficiency (EQE) by 20%, owing to the increased hole concentration in the wells adjacent to the n-side, as confirmed by numerical simulations of carrier distributions across the active region. Doping the second barrier, in addition to the first one, did not further enhance the EQE, which likely indicates compensation of improved hole injection by degradation of the active region quality due to Mg doping. Both LEDs with Mg δ-doped barriers effectively suppress the drop of efficiency at high injection when compared to the reference sample, and the onset of EQE peak roll-off shifts from ∼80 A/cm{sup 2} in the reference LED to ∼120 A/cm{sup 2} in the LEDs with Mg δ-doped barriers.

  10. First-principles study of the effect of B/N doping in TiO2 thin films for visible light photo-catalysis

    NASA Astrophysics Data System (ADS)

    Ovali, Rasim Volga; Uddin, Md. Nizam; Bengu, Erman; Gulseren, Oguz

    2014-05-01

    Anatase phase of titanium dioxide (TiO2) , a non-toxic and biocompatible wide-band gap semiconductor, when irradiated with a suitable wavelength light is known to facilitate chemical processes on its surface including degradation reactions. In addition, TiO2 is one of the most important and widely investigated photo-catalyst materials. In this work several atomic models for B/N doping have been used to investigate the effect of doping on electronic structure and density of states of TiO2 through ab-initio density functional theory calculations. The results showed that doping with B and/or N induced a) band gap narrowing (red shift of the absorbance spectra to the visible light region) and b) formation of midgap states especially in case of N interstitial model. These results also supported the observed synergistic effects of B/N doping for higher photo-degradation activity. These computational findings supported the experimental data by indicating the possible routes that can be responsible for the improvement of the photo-catalytic activity in TiO2 due to B and N doping in our experiments. TUBITAK Grant No: TBAG 112T771, TUBITAK Grant No: TBAG 110T394.

  11. Adsorption and photocatalytic degradation of pharmaceuticals and pesticides by carbon doped-TiO2 coated on zeolites under solar light irradiation.

    PubMed

    An, Ye; de Ridder, David Johannes; Zhao, Chun; Schoutteten, Klaas; Bussche, Julie Vanden; Zheng, Huaili; Chen, Gang; Vanhaecke, Lynn

    2016-01-01

    To evaluate the performance of zeolite-supported carbon-doped TiO(2) composite catalysts toward target pollutants under solar light irradiation, the adsorption and photocatalytic degradation of 18 pharmaceuticals and pesticides with distinguishing features (molecular size and volume, and photolysis) were investigated using mordenite zeolites with SiO(2)/Al(2)O(3) ratios of 18 and 240. Different quantities of carbon-doped TiO(2) were coated on the zeolites, and then the finished composite catalysts were tested in demineralized, surface, and hospital wastewater samples, respectively. The composite photocatalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, and surface area and porosity analyses. Results showed that a dispersed layer of carbon-doped TiO(2) is formed on the zeolite surface; this layer blocks the micropores of zeolites and reduces their surface area. However, these reductions did not significantly affect adsorption onto the zeolites. Our results demonstrated that zeolite-supported carbon-doped TiO(2) systems can effectively degrade 18 pharmaceuticals and pesticides in demineralized water under natural and simulated solar light irradiation. In surface and hospital wastewaters, zeolite-supported carbon-doped TiO(2) systems present excellent anti-interference capability against radical scavengers and competitive organics for pollutants removal, and higher pollutants adsorption on zeolites evidently enhances the removal rate of target pollutants in surface and hospital wastewater samples with a complicated matrix.

  12. Facile route to fabricate carbon-doped TiO2 nanoparticles and its mechanism of enhanced visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Huang, Gui-Fang; Li, Dongfeng; Zhou, Bing-Xin; Chang, Shengli; Pan, Anlian; Huang, Wei-Qing

    2016-12-01

    High-efficiency photocatalysis requires wide photoresponse range and effective separation of photogenerated charges to fully utilize solar energy. Exploring the simple and cheap methods to synthesize efficient photocatalysts is still a challenging issue. Herein, we report a facile and simple room-temperature hydrolysis method using glucose as carbon source to prepare visible light-active C-doped TiO2 photocatalyst. This approach features low-cost, reliable, and easily upscalable. It is found that C atoms have been incorporated into the interstitial position of anatase TiO2 lattice and distributed homogeneously throughout the surface of TiO2 nanoparticles. The appropriate C doping can greatly improve the separation of photogenerated electron-hole pairs in C-doped TiO2. The C-doped TiO2 samples exhibit enhanced photocatalytic activity with the degradation efficiency under UV and visible light irradiation, which is much faster than that of pure TiO2. The mechanism of the enhanced photocatalytic activity is discussed in detail, which is confirmed by using different scavengers. The work provides a simple and useful way to prepare C-doped wide-gap semiconductors with enhanced photocatalytic activity.

  13. Improvement of device efficiency for blue organic light emitting diodes by controlling the Cs2CO3-doped electron transport layer

    NASA Astrophysics Data System (ADS)

    Fu, Richard; Shi, Jianmin; Forsythe, Eric; Blomquist, Steven; Srour, Merric; Morton, David

    2014-01-01

    The electronic transport properties of 1, 3, 5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBI) electron transporting layers (ETLs) have been investigated as a function of cesium carbonate (Cs2CO3) doping for organic light-emitting diodes (OLEDs). The current density-voltage and light emission characteristics were measured as a function of the Cs2CO3-doped ETL thickness. Cs2CO3-doped TPBI decreased OLED operating voltage by 26% and increased device luminance by 17% in a wide concentration range (3.5% to 10.5%) compared to undoped devices. The effects of 7% Cs2CO3-doped ETL thickness indicated that the operating voltage continuously decreased to 37% when the ETL thickness increased to 600 Å and luminance output continued to increase to 21% at ETL thickness 525 Å. The blue OLED can be optimized by adjusting the thicknesses of Cs2CO3-doped TPBI ETL to balance the electron and hole injection.

  14. Degradation of selected industrial dyes using Mg-doped TiO2 polyscales under natural sun light as an alternative driving energy

    NASA Astrophysics Data System (ADS)

    Shivaraju, H. P.; Midhun, G.; Anil Kumar, K. M.; Pallavi, S.; Pallavi, N.; Behzad, Shahmoradi

    2017-03-01

    Designing photocatalytic materials with modified functionalities for the utilization of renewable energy sources as an alternative driving energy has attracted much attention in the area of sustainable wastewater treatment applications. Catalyst-assisted advanced oxidation process is an emerging treatment technology for organic pollutants and toxicants in industrial wastewater. Preparation of visible-light-responsive photocatalyst such as Mg-doped TiO2 polyscales was carried out under mild sol-gel technique. Mg-doped TiO2 polyscales were characterized by powder XRD, SEM, FTIR, and optical and photocatalytic activity techniques. The Mg-doped TiO2 showed a mixed phase of anatase and rutile with an excellent crystallinity, structural elucidations, polyscales morphology, consequent shifting of bandgap energy and adequate photocatalytic activities under visible range of light. Mg-doped TiO2 polyscales were investigated for their efficiencies in the degradation of most commonly used industrial dyes in the real-time textile wastewater. Mg-doped TiO2 polyscales showed excellent photocatalytic degradation efficiency in both model industrial dyes (65-95%) and textile wastewater (92%) under natural sunlight as an alternative and renewable driving energy.

  15. No drain, autologous transfusion drain or suction drain? A randomised prospective study in total hip replacement surgery of 168 patients.

    PubMed

    Cheung, Graham; Carmont, Michael R; Bing, Andrew J F; Kuiper, Jan-Herman; Alcock, Robert J; Graham, Niall M

    2010-10-01

    We performed a prospective, randomised controlled trial to assess the differences in the use of a conventional suction drain, an Autologous Blood Transfusion (ABT) drain and no drain, in 168 patients. There was no significant difference between the drainage from ABT drains ( mean : 345 ml) and the suction drain (314 ml). Forty percent of patients receiving a suction drain had a haemoglobin level less than 10 g/dL at 24 hours, compared to 35% with no drain and 28% with an ABT drain. Patients that had no drains had wounds that were dry significantly sooner, mean 3.0 days compared to a mean of 3.9 days with an ABT drain and a mean of 4 days with a suction drain. Patients that did not have a drain inserted stayed in hospital a significantly shorter period of time, compared with drains. We feel the benefits of quicker drying wounds, shorter hospital stays and the economic savings justify the conclusion that no drain is required after hip replacement.

  16. Improved performance of organic light-emitting diodes fabricated on Al-doped ZnO anodes incorporating a homogeneous Al-doped ZnO buffer layer grown by atomic layer deposition.

    PubMed

    Choi, Yong-June; Gong, Su Cheol; Park, Chang-Sun; Lee, Hong-Sub; Jang, Ji Geun; Chang, Ho Jung; Yeom, Geun Young; Park, Hyung-Ho

    2013-05-01

    In this work, we investigated the use of a homogeneous Al-doped zinc oxide (AZO) buffer layer to improve the performance of an organic light-emitting diode (OLED) device fabricated on an AZO anode. For this, 10-nm-thick AZO buffer layers with Al doping concentrations of 3.1, 4.1, and 5.1 at % were grown on 140-nm-thick AZO anode films containing 2.1 at % Al by atomic layer deposition. The electrical resistivity of the AZO anode with a homogeneous AZO buffer layer decreased with an increase in Al doping concentration up to 4.1 at %; however, the resistivity increased at higher doping concentrations in the AZO buffer layer. On the other hand, the work functions of the AZO anode with the AZO buffer layer containing various Al doping concentrations gradually increased with an increase in Al doping concentration from 3.1 to 5.1 at %. Therefore, the best film properties were obtained for an AZO anode with an AZO buffer layer containing 4.1 at % Al, and the work function value for this film was 4.64 eV. The highest luminance and current efficiency values were optimized to be 20290 cd/m(2) and 13.4 cd/A, respectively, with the OLED device composed of a DNTPD/TAPC/Bebq2:10% doped RP-411/Bphen/LiF/Al structure on an AZO anode with an AZO buffer layer containing 4.1 at % Al.

  17. Visible light absorption ability and photocatalytic oxidation activity of various interstitial N-doped TiO2 prepared from different nitrogen dopants.

    PubMed

    Ananpattarachai, Jirapat; Kajitvichyanukul, Puangrat; Seraphin, Supapan

    2009-08-30

    Nitrogen-doped TiO(2) was developed to enable photocatalytic reactions using the visible range of the solar spectrum. This work reports on the synthesis, characterisation and kinetic study of interstitial N-doped TiO(2) prepared by the sol-gel method using three different types of nitrogen dopants: diethanolamine, triethylamine and urea. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-visible spectroscopy were used to analyse the titania. Different interstitial N-doped TiO(2) properties, such as absorption ability in the UV-visible light region, redshift in adsorption edge, good crystallisation and composition ratio of titania structures (anatase and rutile) could be obtained from different nitrogen dopants. Amongst investigated nitrogen precursors, diethanolamine provided the highest visible light absorption ability of interstitial N-doped TiO(2) with the smallest energy bandgap and the smallest anatase crystal size, resulting in the highest efficiency in 2-chlorophenol degradation. The photocatalytic activity of all N-doped TiO(2) can be arranged in the following order: TiO(2)/diethanolamine>TiO(2)/triethylamine>TiO(2)/urea>un-doped TiO(2). The initial rate of 2-chlorophenol degradation using the interstitial N-doped TiO(2) with diethanolamine was 0.59 mg/L-min and the kinetic constant was 2.34 x 10(-2)min(-1) with a half-life of 98 min. In all cases, hydroquinone was detected as a major intermediate in the degradation of 2-chlorophenol.

  18. Design of N-doped anatase TiO2 photocatalyst with visible-light-response based on Ti-O bond weakening

    NASA Astrophysics Data System (ADS)

    Yin, L.-C.; Liu, G.; Cheng, H.-M.; Advanced Carbon Division Team

    2013-03-01

    Nitrogen bulk doping is an effective strategy to change the electronic structures of anatase TiO2 photocatalyst for visible light response improvement. Unfortunately, it is hard to achieve nitrogen bulk doping in practice, due to both limited thermodynamic solubility of substitutional nitrogen and N-induced recombination centers. It remains challenging yet highly desirable to develop new doping approach to increase nitrogen solubility in bulk. This challenge is originally stemmed from both strong Ti-O bond and charge difference (O2- versus N3-) between lattice oxygen and nitrogen dopant. In this work, we propose a new doping approach to promote the bulk substitution of lattice oxygen with nitrogen in bulk anatase TiO2, based on the Ti-O bond weakening by pre-implanted interstitial boron.1 By using the first-principles calculations, we study the interstitial boron induced Ti-O bonding weakening and the thermodynamics/kinetics changes for nitrogen bulk doping.2 In experiment, we realize to synthesize a bulk gradient B-N co-doping red anatase TiO2 microsphere which has an extended absorption edge up to ca. 700 nm covering the full visible light spectrum and has a bandgap varying from 1.94 eV on its surface to 3.22 eV in its core by gradually elevating VBM. This approach could be extended to modify other electronic materials that demand bulk substitutional doping. 1. G. Liu, J. Pan, L. C. Yin et al., Adv. Funct. Mater., 2012, 22, 3233. 2. G. Liu, L. C. Yin, J. Q. Wang et al., Energy Environ. Sci. 2012, 5, 9603. Financial support from Ministry of Science and Technology of China (no. 2009CB220001), NSFC (no. 50921004, 51002160, 21090343, 51172243, 51202255), CAS China (KJCX2-YW-H21-01).

  19. Visible-light-driven photocatalytic performance of nitrogen-doped Ti{sub 1−x}Zr{sub x}O{sub 2} solid solution

    SciTech Connect

    Gao, Bifen; Luo, Xiuzhen; Fu, Hao; Lin, Bizhou; Chen, Yilin; Gu, Zhanjun

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Dual modifications on the energy band of TiO{sub 2} are achieved by N and Zr co-doping. ► Nitrogen and zirconium dopants have different doping positions in the catalyst. ► A synergic impact of nitrogen and zirconium on photocatalytic activity is observed. ► A mechanism for the high performance of nitrogen-doped Ti{sub 1−x}Zr{sub x}O{sub 2} solid solution is proposed. -- Abstract: Nitrogen-doped Ti{sub 1−x}Zr{sub x}O{sub 2} solid solutions have been synthesized by a multi-step sol–gel process followed by hydrothermal treatment in ammonia solution. XRD, XPS and UV–vis diffuse reflectance analyses indicated that nitrogen was doped in the surface layer of catalyst, introducing surface states located close to valence band. However, Zr{sup 4+} was successfully incorporated into the bulk lattice of TiO{sub 2} so as to induce the up-shift of conduction band. Compared to pristine TiO{sub 2} and nitrogen-doped TiO{sub 2}, nitrogen-doped Ti{sub 1−x}Zr{sub x}O{sub 2} exhibited much higher efficiency for the degradation of Acid Red 88 solution and gaseous benzene under visible light irradiation, attributed to the synergetic effect of nitrogen and zirconium on the energy band. Specifically, the presence of surface states in the band gap enabled the extended visible light response and the up-shift of conduction band facilitated the excited electron interfacial transfer and hence suppressed efficiently the recombination of charge carriers.

  20. Energy-level matching of Fe(III) ions grafted at surface and doped in bulk for efficient visible-light photocatalysts.

    PubMed

    Liu, Min; Qiu, Xiaoqing; Miyauchi, Masahiro; Hashimoto, Kazuhito

    2013-07-10

    Photocatalytic reaction rate (R) is determined by the multiplication of light absorption capability (α) and quantum efficiency (QE); however, these two parameters generally have trade-off relations. Thus, increasing α without decreasing QE remains a challenging issue for developing efficient photocatalysts with high R. Herein, using Fe(III) ions grafted Fe(III) doped TiO2 as a model system, we present a novel method for developing visible-light photocatalysts with efficient R, utilizing the concept of energy level matching between surface-grafted Fe(III) ions as co-catalysts and bulk-doped Fe(III) ions as visible-light absorbers. Photogenerated electrons in the doped Fe(III) states under visible-light efficiently transfer to the surface grafted Fe(III) ions co-catalysts, as the doped Fe(III) ions in bulk produced energy levels below the conduction band of TiO2, which match well with the potential of Fe(3+)/Fe(2+) redox couple in the surface grafted Fe(III) ions. Electrons in the surface grafted Fe(III) ions efficiently cause multielectron reduction of adsorbed oxygen molecules to achieve high QE value. Consequently, the present Fe(III)-FexTi1-xO2 nanocomposites exhibited the highest visible-light R among the previously reported photocatalysts for decomposition of gaseous organic compounds. The high R can proceed even under commercial white-light emission diode irradiation and is very stable for long-term use, making it practically useful. Further, this efficient method could be applied in other wide-band gap semiconductors, including ZnO or SrTiO3, and may be potentially applicable for other photocatalysis systems, such as water splitting, CO2 reduction, NOx removal, and dye decomposition. Thus, this method represents a strategic approach to develop new visible-light active photocatalysts for practical uses.

  1. Luminescence studies on Dy3+ doped calcium boro-tellurite glasses for White light applications

    NASA Astrophysics Data System (ADS)

    Karthikeyan, P.; Vijayakumar, R.; Marimuthu, K.

    2017-09-01

    A new series of Dy3+ doped calcium boro-tellurite glasses have been prepared by melt quenching technique and their spectroscopic properties were studied through FTIR, absorption luminescence and lifetime spectral measurements. FTIR studies have been made to explore the presence of various stretching and bending vibrations of different borate and tellurite groups in the prepared glasses. The bonding parameter values were estimated from the absorption band positions using Nephelauxetic ratios to examine the nature of the metal-ligand bond. The optical band gap and Urbach energy (ΔE) values were obtained from the absorption spectra to explore the electronic band structure of the studied glasses. Judd-Ofelt (JO) theory have been used to determine the JO intensity parameters (Ω2, Ω4, Ω6) following the least square fitting procedure between the experimental and calculated oscillator strength values. The luminescence spectra of the Dy3+ doped calcium boro-tellurite glasses exhibit two intense emission bands corresponding to the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions. Further, they exhibit less intense emission band due to the 4F9/2→6H11/2 transition. Luminescence spectra were characterized through CIE 1931 chromaticity diagram to obtain the dominant emission color of the prepared glasses. The JO intensity parameters and refractive index values have been used to calculate the radiative parameters such as transition probabilities (AR), branching ratios (βR) and stimulated emission cross-section (σPE) values for the observed transitions in the luminescence spectra. The decay curves of all the studied glasses found to exhibit non-exponential behavior and further to understand the energy transfer process takes place between the Dy3+ ions, the decay curves were fitted to the Inokuti-Hirayama (IH) model. The structural and optical properties of the Dy3+ doped calcium boro-tellurite glasses have been studied as a function of different metal cations (Zn, Cd, Pb and

  2. Influence of the thickness and doping of the emission layer on the performance of organic light-emitting diodes with PiN structure

    NASA Astrophysics Data System (ADS)

    Huang, Jingsong; Blochwitz-Nimoth, Jan; Pfeiffer, Martin; Leo, Karl

    2003-01-01

    We have studied the behavior of various intrinsic emission zones on the characteristics of organic light-emitting diodes with a p-doped hole-transport layer and an n-doped electron-transport layer based on our previous work [J. S. Huang, M. Pfeiffer, A. Werner, J. Blochwitz, K. Leo, and S. Liu, Appl. Phys. Lett. 80, 139 (2002)]. This configuration is referred to as a PiN structure. Because the p- and n-doped regions occupy nearly 80% of the total thickness in our PiN device, the intrinsic region becomes a narrow layer between two doped regions. This intrinsic region includes the region where the radiative recombination occurs. Thus, the nature of this layer plays an important role in determining the actual device performance. Employing 8-tris-hydroxyquinoline aluminum as an emitter, we investigated the influence of the thickness of the emitter layer on the performance of the device. The optimum thickness of the emitter layer is found to be 20 nm. Combining the fluorescence dye doping method, we have optimized the PiN structure device. Two emitter systems have been used: Alq3 doped with two highly fluorescent laser dyes, Quinacridone or Coumarin 6, respectively. We have demonstrated the influence of the thickness and the doping of the emission zone on the characteristics of a doped emitter device with PiN structure, and obtained higher-efficiency PiN structure devices. The different properties of PiN devices corresponding to two different emitter dopants with different trapping effect are also discussed.

  3. New insight into the enhanced visible-light photocatalytic activities of B-, C- and B/C-doped anatase TiO2 by first-principles.

    PubMed

    Yu, Jiaguo; Zhou, Peng; Li, Qin

    2013-08-07

    The geometry structures, formation energies and electronic properties of the B-, C- and B/C-doped anatase TiO2 were investigated by the density functional theory (DFT) calculations of first-principles. The results indicated that the visible-light absorption and photocatalytic activities of the B-, C- and B/C-doped anatase TiO2 were not only influenced by the energy gaps (Eg) and the distributions of impurity states, but also affected by the locations of Fermi levels (EF) and the energies of the edges of band gaps (Ev for the top of valence bands and Ec for the bottom of conduction bands). However, the above four factors changed with the doped models of TiO2. The impurity states in the band gaps reduced the maximum energy gaps in the band gaps, which is responsible for the absorption of visible light. The Fermi levels at the bottom of conduction bands indicated the existence of Ti(3+) ions, which enhanced the separation rates of photogenerated electrons and holes. Further, the energies of the edges of band gaps, determining the dominant types of oxidants (O2(-), hole, ˙OH) in the photocatalytic degradation, were discussed. Moreover, the stability of the doped TiO2 depended on its growth conditions (O-rich or Ti-rich environment). The O-rich growth condition is beneficial to the substitutional B and C atoms to Ti atoms, while the Ti-rich growth condition is favorable to the other doped TiO2 including the most stable co-doped TiO2 with the interstitial B atom and the substitutional C atom to O atom. In addition, our results also showed that the B/C-doped TiO2 inherited the partial electronic properties of single-doped TiO2, but also exhibited many new electronic properties, implying that the electronic properties of co-doped systems are not a mechanical mixture of those of both single-doped systems.

  4. Pink light emitting long-lasting phosphorescence in Sm 3+-doped CdSiO 3

    NASA Astrophysics Data System (ADS)

    Lei, Bingfu; Liu, Yingliang; Liu, Jie; Ye, Zeren; Shi, Chunshan

    2004-04-01

    Novel pink light emitting long-lasting afterglow CdSiO 3:Sm 3+ phosphors are prepared by the conventional high-temperature solid-state method and their luminescent properties are investigated. XRD and photoluminescence (PL) spectra are used to characterize the synthesized phosphors. The phosphors are well crystallized by calcinations at 1050°C for 5 h. These phosphors emit pink light and show long-lasting phosphorescence after they are excited with 254 nm ultraviolet light. The phosphorescence lasts for nearly 5 h in the light perception of the dark-adapted human eye (0.32 mcd/m 2). The phosphorescence mechanism is also investigated. All the results indicate that these phosphors have promising potential practical applications.

  5. Spectral investigations on Eu(3+) ,Sm(3+) -doped and Sm(3+) /Eu(3+) co-doped potassium-fluoro-phosphate glass emitting intense orange-red for lighting applications.

    PubMed

    Anil Kumar, Kapuluri; Babu, Singarapu; Reddy Prasad, Vasanthapalli; Damodaraiah, Samadam; Ratnakaram, Yadala Chenchu

    2017-06-14

    Potassium fluoro-phosphate (KFP) glass singly doped with different concentrations of europium (Eu(3+) ) or samarium (Sm(3+) ) or co-doped (Sm(3+) /Eu(3+) ) was prepared, and their luminescence spectra were investigated. The phase composition of the product was verified by X-ray diffraction analysis. Optical transition properties of Eu(3+) in the studied potassium phosphate glass were evaluated in the framework of the Judd-Ofelt theory. The radiative transition rates (AR ), fluorescence branching ratios (β), stimulated emission cross-sections (σe ) and lifetimes (τexp ) for certain transitions or levels were evaluated. Red emission of Eu(3+) was exhibited mainly by the (5) D0 →(7) F2 transition located at 612 nm. Concentration quenching and energy transfer were observed from fluorescence spectra and decay curves, respectively. It was found that the lifetimes of the (5) D0 level increased with increase in concentration and then decreased. By co-doping with Sm(3+) , energy transfer from Sm(3+) to Eu(3+) occurred and contributed to the enhancement in emission intensity. Intense orange-red light emission was obtained upon sensitizing with Sm(3+) in KFP glass. This approach shows significant promise for use in reddish-orange lighting applications. The optimized properties of the Sm(3+) /Eu(3+) co-doped potassium phosphate glass might be promising for optical materials. Copyright © 2017 John Wiley & Sons, Ltd.

  6. Visible-Light-Responsive Photocatalysis: Ag-Doped TiO2 Catalyst Development and Reactor Design Testing

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Hintze, Paul E.; Meier, Anne; Shah, Malay G.; Devor, Robert W.; Surma, Jan M.; Maloney, Phillip R.; Bauer, Brint M.; Mazyck, David W.

    2016-01-01

    In recent years, the alteration of titanium dioxide to become visible-light-responsive (VLR) has been a major focus in the field of photocatalysis. Currently, bare titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Hg-vapor fluorescent light sources are used in photocatalytic oxidation (PCO) reactors to provide adequate levels of ultraviolet light for catalyst activation; these mercury-containing lamps, however, hinder the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure. VLR-TiO2 would allow for use of ambient visible solar radiation or highly efficient visible wavelength LEDs, both of which would make PCO approaches more efficient, flexible, economical, and safe. Over the past three years, Kennedy Space Center has developed a VLR Ag-doped TiO2 catalyst with a band gap of 2.72 eV and promising photocatalytic activity. Catalyst immobilization techniques, including incorporation of the catalyst into a sorbent material, were examined. Extensive modeling of a reactor test bed mimicking air duct work with throughput similar to that seen on the International Space Station was completed to determine optimal reactor design. A bench-scale reactor with the novel catalyst and high-efficiency blue LEDs was challenged with several common volatile organic compounds (VOCs) found in ISS cabin air to evaluate the system's ability to perform high-throughput trace contaminant removal. The ultimate goal for this testing was to determine if the unit would be useful in pre-heat exchanger operations to lessen condensed VOCs in recovered water thus lowering the burden of VOC removal for water purification systems.

  7. Pyramidal defects in Mg-doped GaN in light of strain-energy minimization

    NASA Astrophysics Data System (ADS)

    Lee, Dong Nyung

    2011-12-01

    The planar segregation gives rise to stress and strain fields which are approximated by a uniaxial character in a displacement controlled system. In this condition, the elastic strain energy is proportional to Young's modulus. Young's modulus of GaN is minimized when the directions normal to a conical segregation surface make about 48° with the c-axis of hexagonal GaN, which is close to the angle 47.3° between the c-axis and the directions normal to the {112¯3} planes. This implies that the formation of pyramidal defects in magnesium-doped GaN can be a compromise between minimization of the elastic strain energy due to segregation of magnesium and the planar segregation.

  8. Emerging cool white light emission from Dy(3+) doped single phase alkaline earth niobate phosphors for indoor lighting applications.

    PubMed

    Vishwakarma, Amit K; Jha, Kaushal; Jayasimhadri, M; Sivaiah, B; Gahtori, Bhasker; Haranath, D

    2015-10-21

    Single-phase cool white-light emitting BaNb2O6:Dy(3+) phosphors have been synthesized via a conventional solid-state reaction method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) observations and spectrofluorophotometric measurements. XRD and Rietveld structural refinement studies confirm that all the samples exhibit pure orthorhombic structure [space group -C2221(20)]. SEM observations reveal the dense particle packaging with irregular morphology in a micron range. The as-prepared phosphors exhibit blue (482 nm) and yellow (574 nm) emissions under 349, 364, 386 and 399 nm excitations corresponding to (4)F9/2→(6)HJ (J = 15/2, 13/2) transitions of Dy(3+) ions. The energy transfer mechanism between Dy(3+) ions has been studied in detail and the luminescence decay lifetime for the (4)F9/2 level was found to be around 146.07 μs for the optimized phosphor composition. The calculated Commission Internationale de L'Eclairage (CIE) chromaticity coordinates for the optimized phosphor are (x = 0.322, y = 0.339), which are close to the National Television Standard Committee (NTSC) (x = 0.310, y = 0.316) coordinates. The values of CIE chromaticity coordinates and correlated color temperature (CCT) of 5907 K endorse cool white-light emission from the phosphor. The study reveals that BaNb2O6:Dy(3+) phosphor could be a potential candidate for near ultra-violet (NUV) excited white-LED applications.

  9. Er-doped light emitting slot waveguides monolithically integrated in a silicon photonic chip.

    PubMed

    Ramírez, J M; Ferrarese Lupi, F; Berencén, Y; Anopchenko, A; Colonna, J P; Jambois, O; Fedeli, J M; Pavesi, L; Prtljaga, N; Rivallin, P; Tengattini, A; Navarro-Urrios, D; Garrido, B

    2013-03-22

    An integrated erbium-based light emitting diode has been realized in a waveguide configuration allowing 1.54 μm light signal routing in silicon photonic circuits. This injection device is based on an asymmetric horizontal slot waveguide where the active slot material is Er(3+) in SiO2 or Er(3+) in Si-rich oxide. The active horizontal slot waveguide allows optical confinement, guiding and lateral extraction of the light for on-chip distribution. Light is then coupled through a taper section to a passive Si waveguide terminated by a grating which extracts (or inserts) the light signal for measuring purposes. We measured an optical power density in the range of tens of μW/cm(2) which follows a super-linear dependence on injected current density. When the device is biased at high current density, upon a voltage pulse (pump signal), free-carrier and space charge absorption losses become large, attenuating a probe signal by more than 60 dB/cm and thus behaving conceptually as an electro-optical modulator. The integrated device reported here is the first example, still to be optimized, of a fundamental block to realize an integrated silicon photonic circuit with monolithic integration of the light emitter.

  10. Adsorption and solar light decomposition of acetone on anatase TiO2 and niobium doped TiO2 thin films.

    PubMed

    Mattsson, Andreas; Leideborg, Michael; Larsson, Karin; Westin, Gunnar; Osterlund, Lars

    2006-01-26

    Adsorption and solar light decomposition of acetone was studied on nanostructured anatase TiO2 and Nb-doped TiO2 films made by sol-gel methods (10 and 20 mol % NbO2.5). A detailed characterization of the film materials show that films contain only nanoparticles with the anatase modification with pentavalent Nb oxide dissolved into the anatase structure, which is interpreted as formation of substituted Nb=O clusters in the anatase lattice. The Nb-doped films displayed a slight yellow color and an enhanced the visible light absorption with a red-shift of the optical absorption edge from 394 nm for the pure TiO2 film to 411 nm for 20 mol % NbO2.5. In-situ Fourier transform infrared (FTIR) transmission spectroscopy shows that acetone adsorbs associatively with eta1-coordination to the surface cations on all films. On Nb-doped TiO2 films, the carbonyl bonding to the surface is stabilized, which is evidenced by a lowering of the nu(C=O) frequency by about 20 cm(-1) to 1672 cm(-1). Upon solar light illumination acetone is readily decomposed on TiO2, and stable surface coordinated intermediates are formed. The decomposition rate is an order of magnitude smaller on the Nb-doped films despite an enhanced visible light absorption in these materials. The quantum yield is determined to be 0.053, 0.004 and 0.002 for the pure, 10% Nb:TiO2, and 20%Nb:TiO2, respectively. Using an interplay between FTIR and DFT calculations we show that the key surface intermediates are bidentate bridged formate and carbonate, and H-bonded bicarbonate, respectively, whose concentration on the surface can be correlated with their heats of formation and bond strength to coordinatively unsaturated surface Ti and Nb atoms at the surface. The oxidation rate of these intermediates is substantially slower than the initial acetone decomposition rate, and limits the total oxidation rate at t>7 min on TiO2, while no decrease of the rate is observed on the Nb-doped films. The rate of degradation of key surface

  11. Highly Efficient F, Cu doped TiO2 anti-bacterial visible light active photocatalytic coatings to combat hospital-acquired infections

    NASA Astrophysics Data System (ADS)

    Leyland, Nigel S.; Podporska-Carroll, Joanna; Browne, John; Hinder, Steven J.; Quilty, Brid; Pillai, Suresh C.

    2016-04-01

    Bacterial infections are a major threat to the health of patients in healthcare facilities including hospitals. One of the major causes of patient morbidity is infection with Staphylococcus aureus. One of the the most dominant nosocomial bacteria, Methicillin Resistant Staphylococcus aureus (MRSA) have been reported to survive on hospital surfaces (e.g. privacy window glasses) for up to 5 months. None of the current anti-bacterial technology is efficient in eliminating Staphylococcus aureus. A novel transparent, immobilised and superhydrophilic coating of titanium dioxide, co-doped with fluorine and copper has been prepared on float glass substrates. Antibacterial activity has demonstrated (by using Staphylococcus aureus), resulting from a combination of visible light activated (VLA) photocatalysis and copper ion toxicity. Co-doping with copper and fluorine has been shown to improve the performance of the coating, relative to a purely fluorine-doped VLA photocatalyst. Reductions in bacterial population of log10 = 4.2 under visible light irradiation and log10 = 1.8 in darkness have been achieved, compared with log10 = 1.8 under visible light irradiation and no activity, for a purely fluorine-doped titania. Generation of reactive oxygen species from the photocatalytic coatings is the major factor that significantly reduces the bacterial growth on the glass surfaces.

  12. Highly Efficient F, Cu doped TiO2 anti-bacterial visible light active photocatalytic coatings to combat hospital-acquired infections

    PubMed Central

    Leyland, Nigel S.; Podporska-Carroll, Joanna; Browne, John; Hinder, Steven J.; Quilty, Brid; Pillai, Suresh C.

    2016-01-01

    Bacterial infections are a major threat to the health of patients in healthcare facilities including hospitals. One of the major causes of patient morbidity is infection with Staphylococcus aureus. One of the the most dominant nosocomial bacteria, Methicillin Resistant Staphylococcus aureus (MRSA) have been reported to survive on hospital surfaces (e.g. privacy window glasses) for up to 5 months. None of the current anti-bacterial technology is efficient in eliminating Staphylococcus aureus. A novel transparent, immobilised and superhydrophilic coating of titanium dioxide, co-doped with fluorine and copper has been prepared on float glass substrates. Antibacterial activity has demonstrated (by using Staphylococcus aureus), resulting from a combination of visible light activated (VLA) photocatalysis and copper ion toxicity. Co-doping with copper and fluorine has been shown to improve the performance of the coating, relative to a purely fluorine-doped VLA photocatalyst. Reductions in bacterial population of log10 = 4.2 under visible light irradiation and log10 = 1.8 in darkness have been achieved, compared with log10 = 1.8 under visible light irradiation and no activity, for a purely fluorine-doped titania. Generation of reactive oxygen species from the photocatalytic coatings is the major factor that significantly reduces the bacterial growth on the glass surfaces. PMID:27098010

  13. Hydrothermal fabrication of N-doped (BiO)2CO3: Structural and morphological influence on the visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Dong, Fan; Wang, Rui; Li, Xinwei; Ho, Wing-Kei

    2014-11-01

    Various 3D N-doped (BiO)2CO3 (N-BOC) hierarchical superstructures self-assembled with 2D nanosheets were fabricated by one-step hydrothermal treatment of bismuth citrate and urea. The as-obtained samples were characterized by XRD, XPS, FT-IR, SEM, N2 adsorption-desorption isotherms and UV-vis DRS. The hydrothermal temperature plays a crucial role in tuning the crystal and morphological structure of the samples. Adjusting the reaction temperature to 150, 180 and 210 °C, we obtained N-doped (BiO)2CO3 samples with corresponding attractive persimmon-like, flower-like and nanoflakes nano/microstructures. The photocatalytic activities of the samples were evaluated by removal of NO under visible and solar light irradiation. The results revealed that the N-doped (BiO)2CO3 hierarchical superstructures showed enhanced visible light photocatalytic activity compared to pure (BiO)2CO3 and TiO2-based visible light photocatalysts. The outstanding photocatalytic performance of N-BOC samples can be ascribed to the doped nitrogen and the special hierarchical structure. The present work could provide new perspectives in controlling the morphological structure and photocatalytic activity of photocatalyst for better environmental pollution control.

  14. 38. View of 6' valve for draining Wolslegal Basin, looking ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    38. View of 6' valve for draining Wolslegal Basin, looking south from north side of the basin. Photo by Brian C. Morris, Puget Power, 1989. - Puget Sound Power & Light Company, White River Hydroelectric Project, 600 North River Avenue, Dieringer, Pierce County, WA

  15. Highly strained channel with low-resistivity carbon-doped source/drain formed by cascade C7Hx implantation followed by rapid solid-phase epitaxy and laser annealing for n-channel metal-oxide-semiconductor field-effect transistor

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tadashi; Kawasaki, Yoji; Yamashita, Tomohiro; Nishida, Yukio; Mizuo, Mariko; Maekawa, Kazuyoshi; Fujisawa, Masahiko

    2015-03-01

    We show the systematical investigation results of the effects of the implanted ion dose of P or As under various solid-phase epitaxy (SPE) conditions on the local stress in channel regions in metal-oxide-semiconductor field-effect transistor (MOSFET) structures, and on sheet resistance and strain in carbon-doped source/drain (Si:C-S/D) layers. P or As substitution is in conflict with C substitution in Si:C layers during SPE. Furthermore, the amount of P incorporated instead of C into the Si lattice site is larger than that of As incorporated instead of C. Therefore, low-resistivity Si:C layers with low stress in the case of using P and high-resistivity Si:C layers with high stress in the case of using As are formed by single-step C7Hx implantation with rapid thermal annealing and nonmelt laser annealing, respectively. As a countermeasure, we demonstrate that cascade C7Hx implantation to control the C profiles in Si:C layers is effective for achieving high-strain channels and low-resistivity Si:C-S/D layers. Control of C profiles is a key technology for state-of-the-art complementary MOS devices with Si:C-S/D.

  16. Enhanced Performance of Quantum Dot-Based Light-Emitting Diodes with Gold Nanoparticle-Doped Hole Injection Layer

    NASA Astrophysics Data System (ADS)

    Chen, Fei; Lin, Qingli; Wang, Hongzhe; Wang, Lei; Zhang, Fengjuan; Du, Zuliang; Shen, Huaibin; Li, Lin Song

    2016-08-01

    In this paper, the performance of quantum dot-based light-emitting diodes (QLEDs) comprising ZnCdSe/ZnS core-shell QDs as an emitting layer were enhanced by employing Au-doped poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) hole injection layer (HIL). By varying the concentration and dimension of Au nanoparticle (NP) dopants in PEDOT:PSS, the optimal devices were obtained with ~22-nm-sized Au NP dopant at the concentration with an optical density (OD) of 0.21. Highly bright green QLEDs with a maximum external quantum efficiency (EQE) of 8.2 % and a current efficiency of 29.1 cd/A exhibit 80 % improvement compared with devices without Au NP dopants. The improved performance may be attributed to the significant increase in the hole injection rate as a result of the introduction of Au NPs and the good matching between the resonance frequency of the localized surface plasmon resonance (LSPR) generated by the Au NPs and the emission band of QD layer, as well as the suppressed Auger recombination of QD layer due to the LSPR-induced near-field enhanced radiative recombination rate of excitons. These results are helpful for fabricating high-performance QD-based applications, such as full-color displays and solid-state lighting.

  17. Insight into visible light-driven photocatalytic degradation of diesel oil by doped TiO2-PS floating composites.

    PubMed

    Wang, Xin; Wang, Wei; Wang, Xuejiang; Zhao, Jianfu; Zhang, Jing; Song, Jingke

    2016-09-01

    TiO2-pearlstone (PS) floatable photocatalysts were synthesized using a facile sol-gel method and confirmed by XRD, N2 adsorption-desorption, SEM, EDX, TEM, FT-IR, XPS, and UV-vis DRS measurements. It has been found that the photocatalysts composed of anatase TiO2 deposited on the surface of PS and formed mesoporous structure. By N or B/N doping, the band gap of the photocatalyst has been narrowed. The obtained floatable photocatalysts can be applied to solar light-driven remediation of oil-contaminated water. Diesel oil was chosen as the model pollutant to evaluate the photocatalytic activity. The results showed B/N-TiO2-PS exhibited the highest photocatalytic activity for diesel oil under visible light irradiation, which is 48 % removal rate for 9 h. The reaction rate constant k of B/N-TiO2-PS is 0.08423 h(-1), which is four times larger than that of pure TiO2-PS. Moreover, the characteristic of floatable makes the photocatalysts easier to separate and reuse, which showed great potential for practical applications in the field of environmental cleanup and solar energy conversion.

  18. Electrostatic Discharge Characteristics of InGaN/GaN Light-Emitting Diodes with Si-Doped Graded Superlattice.

    PubMed

    Lee, Kwanjae; Lee, Cheul-Ro; Kim, Jin Soo; Lee, Jin Hong; Lim, Kee Young; Leem, Jae-Young

    2015-10-01

    We report the influences of a Si-doped graded superlattice (SiGSL) on the electrostatic discharge (ESD) characteristics of an InGaN/GaN light-emitting diode (LED). For comparison, a conventional InGaN/GaN LED (C-LED) was also investigated. The luminous efficacy for the SiGSL-LED was 2.68 times stronger than that for the C-LED at the injection current of 20 mA. The resistances estimated from current-voltage (I-V) characteristic curves were 16.5 and 8.8 Ω for the C-LED and SiGSL-LED, respectively. After the ESD treatment at the voltages of 4000 and 6000 V, there was no significant change in the I-V curves for the SiGSL-LED. Also, there was small variation in the I-V characteristics for the SiGSL-LED at the ESD voltage of 8000 V. However, the I-V curves for the C-LED were drastically degraded with increasing ESD voltage. While the light emission was not observed at the injection current of 20 mA from the C-LED sample after the ESD treatment, the emission spectra for the SiGSL-LED sample were clearly measured with the output powers of 10.47, 9.66, and 7.27 mW for the ESD voltages of 4000, 6000, and 8000 V respectively.

  19. N-Type Superconductivity in an Organic Mott Insulator Induced by Light-Driven Electron-Doping.

    PubMed

    Suda, Masayuki; Takashina, Naoto; Namuangruk, Supawadee; Kungwan, Nawee; Sakurai, Hidehiro; Yamamoto, Hiroshi M

    2017-09-01

    The presence of interface dipoles in self-assembled monolayers (SAMs) gives rise to electric-field effects at the device interfaces. SAMs of spiropyran derivatives can be used as photoactive interface dipole layer in field-effect transistors because the photochromism of spiropyrans involves a large dipole moment switching. Recently, light-induced p-type superconductivity in an organic Mott insulator, κ-(BEDT-TTF)2 Cu[N(CN)2 ]Br (κ-Br: BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene) has been realized, thanks to the hole carriers induced by significant interface dipole variation in the spiropyran-SAM. This report explores the converse situation by designing a new type of spiropyran monolayer in which light-induced electron-doping into κ-Br and accompanying n-type superconducting transition have been observed. These results open new possibilities for novel electronics utilizing a photoactive SAMs, which can design not only the magnitude but also the direction of photoinduced electric-fields at the device interfaces. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Bichromatic coherent random lasing from dye-doped polymer stabilized blue phase liquid crystals controlled by pump light polarization

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Wang, Meng; Yang, Mingchao; Shi, Li-Jie; Deng, Luogen; Yang, Huai

    2016-09-01

    In this paper, we investigate the bichromatic coherent random lasing actions from the dye-doped polymer stabilized blue phase liquid crystals. Two groups of lasing peaks, of which the full widith at half maximum is about 0.3 nm, are clearly observed. The shorter- and longer-wavelength modes are associated with the excitation of the single laser dye (DCM) monomers and dimers respectively. The experimental results show that the competition between the two groups of the lasing peaks can be controlled by varying the polarization of the pump light. When the polarization of the pump light is rotated from 0° to 90°, the intensity of the shorter-wavelength lasing peak group reduces while the intensity of the longer-wavelength lasing peak group increases. In addition, a red shift of the longer-wavelength modes is also observed and the physical mechanisms behind the red-shift phenomenon are discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474021 and 51333001), the Key Program for International S&T Cooperation Projects of China (Grant No. 2013DFB50340), the Issues of Priority Development Areas of the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120001130005), and the Key (Key Grant) Project of Chinese Ministry of Education (Grant No. 313002).

  1. Food contact surfaces coated with nitrogen-doped titanium dioxide: effect on Listeria monocytogenes survival under different light sources

    NASA Astrophysics Data System (ADS)

    Rodrigues, D.; Teixeira, P.; Tavares, C. J.; Azeredo, J.

    2013-04-01

    Improvement of food safety is a very important issue, and is on the basis of production and application of new/modified food contact surfaces. Titanium dioxide (TiO2) and, more recently, nitrogen-doped titanium dioxide (N-TiO2) coatings are among the possible forms to enhance food contact surfaces performance in terms of higher hygiene and easier sanitation. In this context, the present work aimed at evaluating the bactericidal activity of an N-TiO2 coating on glass and stainless steel under two different sources of visible light - fluorescent and incandescent - and ultraviolet (UV) irradiation. Listeria monocytogenes was chosen as representative of major foodborne pathogens and its survival was tested on N-TiO2 coated coupons. In terms of survival percentage, good results were obtained after exposure of coated surfaces to all light types since, apart from the value obtained after exposing glass to fluorescent light (56.3%), survival rates were always below 50%. However, no effective disinfection was obtained, given that for a disinfectant or sanitizing agent to be claimed as effective it needs to be able to promote at least a 3-log reduction of the microbial load, which was not observed for any of the experimental conditions assessed. Even so, UV irradiation was the most successful on eliminating cells on coated surfaces, since the amount of bacteria was reduced to 1.49 × 106 CFU/ml on glass and 2.37 × 107 on stainless steel. In contrast, both visible light sources had only slightly decreased the amount of viable cells, which remained in the range of 8 log CFU/ml. Hence, although some bactericidal effect was accomplished under visible light, UV was the most effective light source on promoting photocatalytic reactions on N-TiO2 coated coupons and none of the experimental conditions have reached a satisfactory disinfection level. Thus, this surface coating needs further research and improvement in order to become truly effective against foodborne pathogens and

  2. Driving voltage reduction in white organic light-emitting devices from selectively doping in ambipolar blue-emitting layer

    NASA Astrophysics Data System (ADS)

    Hsiao, Chih-Hung; Lin, Chi-Feng; Lee, Jiun-Haw

    2007-11-01

    White organic light-emitting devices (OLEDs) consisting of ambipolar 9,10-bis(2'-naphthyl) anthracene (ADN) as a host of blue-emitting layer (EML) were investigated. A thin codoped layer of yellow 5,6,11,12-Tetraphenylnaphthacene (rubrene) served as a probe for detecting the position of maximum recombination rate in the 4,4'-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl (DPAVBi) doped-ADN EML. Due to the energy barrier and bipolar carrier transport, the maximum recombination rate was found to be close to but not exactly at the interface of the hole-transporting layer and the EML. With appropriate tuning in the thickness, position, and dopant concentrations of the codoped layer (rubrene:DPAVBi:ADN) in the EML, the device driving voltage decreased by 21.7%, nearly 2 V in reduction, due to the increased recombination current from the faster exciton relaxation induced by the yellow dopants. Among the advantages of introducing the codoped layer over conventional single-doped layers are the elimination of the trapping effect to avoid increasing the device driving voltage, the alleviation of the dependence of the recombination zone on the applied voltage for improving color stability, and the utilization of excitons in a more efficient way to enhance device efficiency. Without using any electrically conductive layers such as the p-i-n structure, we were able to successfully generate 112 cd/m2 at 4 V from our white OLED simply by engineering the structure of the EML.

  3. Second-harmonic generation of light at 544 and 272 nm from an ytterbium-doped distributed-feedback fiber laser.

    PubMed

    Herskind, Peter; Lindballe, Jens; Clausen, Christoph; Sørensen, Jens Lykke; Drewsen, Michael

    2007-02-01

    We report external cavity second-harmonic generation of light at 544 and 272 nm based on an ytterbium-doped distributed-feedback fiber laser. The nonlinear crystal used to generate light at 544 nm is LiNbO3, and the maximum output of the cavity is 845 mW, corresponding to a conversion efficiency of 55%. In a second frequency-doubling step, using a beta-BaBa2O4 crystal, we generate up to 115 mW of light at 272 nm with a conversion efficiency of 14%.

  4. p-doping-free InGaN/GaN light-emitting diode driven by three-dimensional hole gas

    SciTech Connect

    Zhang, Zi-Hui; Tiam Tan, Swee; Kyaw, Zabu; Liu, Wei; Ji, Yun; Ju, Zhengang; Zhang, Xueliang; Wei Sun, Xiao; Volkan Demir, Hilmi

    2013-12-23

    Here, GaN/Al{sub x}Ga{sub 1-x}N heterostructures with a graded AlN composition, completely lacking external p-doping, are designed and grown using metal-organic-chemical-vapour deposition (MOCVD) system to realize three-dimensional hole gas (3DHG). The existence of the 3DHG is confirmed by capacitance-voltage measurements. Based on this design, a p-doping-free InGaN/GaN light-emitting diode (LED) driven by the 3DHG is proposed and grown using MOCVD. The electroluminescence, which is attributed to the radiative recombination of injected electrons and holes in InGaN/GaN quantum wells, is observed from the fabricated p-doping-free devices. These results suggest that the 3DHG can be an alternative hole source for InGaN/GaN LEDs besides common Mg dopants.

  5. Cesium hydroxide doped tris-(8-hydroxyquinoline) aluminum as an effective electron injection layer in inverted bottom-emission organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Xiong, Tao; Wang, Fengxia; Qiao, Xianfeng; Ma, Dongge

    2008-06-01

    We demonstrate highly efficient inverted bottom-emission organic light-emitting diodes (IBOLEDs) by using cesium hydroxide (CsOH) doped tris-(8-hydroxyquinoline) aluminum (Alq3) as the electron injection layer on indium tin oxide cathode, which could significantly enhance the electron injection, resulting in a large increase in luminance and efficiency. The maximum luminance, current efficiency, and power efficiency reach 21000cd/cm2, 6.5cd/A, and 3.5lm/W, respectively, which are 40%-50% higher in efficiency than that of IBOLEDs with cesium carbonate (Cs2CO3) doped Alq3 as the electron injection layer, where the efficiencies are only 4.5cd/A and 2.2lm/W. Our results indicate that CsOH doped Alq3 should be an effective electron injection layer on a wide range of electrodes to fabricate high performance OLEDs.

  6. Characteristics of vanadium-doped indium oxide thin films for organic light-emitting diodes fabricated by spray chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Seki, Yoshiyuki; Seki, Shigeyuki; Hoshi, Yoichi; Uchida, Takayuki; Sawada, Yutaka

    2015-04-01

    An indium oxide transparent electrode for organic light-emitting diodes was fabricated by the inexpensive spray chemical vapor deposition method. The high work function (5.1 eV) necessary for a transparent anode and a hole-injection layer was successfully achieved with a vanadium doping concentration of 1.5 at. % V without any significant increase in resistivity and surface roughness or loss of transparency. The effect of vanadium doping on indium oxide was systematically investigated. The resistivity, average transmittance in the visible range, and surface roughness (Ra) were 1.08 × 10-3 Ω·cm, 84%, and 4.0 nm, respectively, for the vanadium-doped indium oxide.

  7. Lanthanide-Doped Upconversion Nanoparticles: Emerging Intelligent Light-Activated Drug Delivery Systems.

    PubMed

    Bagheri, Ali; Arandiyan, Hamidreza; Boyer, Cyrille; Lim, May

    2016-07-01

    The development of drug delivery systems (DDSs) using near infrared (NIR) light and upconversion nanoparticles (UCNPs) has generated intensive interest over the past five years. These NIR-initiated DDSs not only offer a high degree of spatial and temporal determination of therapeutic release but also provide precise control over the released dosage. Furthermore, these nanoplatforms confer several advantages over conventional light-based DDSs-NIR offers better tissue penetration depth and a reduced risk of cellular photo-damage caused by exposure to light at high-energy wavelengths (e.g., ultraviolet light, <400 nm). The development of DDSs that can be activated by low intensity NIR illumination is highly desirable to avoid exposing living tissues to excessive heat that can limit the in vivo application of these DDSs. This encompasses research in three directions: (i) enhancing the quantum yield of the UCNPs; (ii) incorporation of photo-responsive materials with red-shifted absorptions into the UCNPs; and (iii) tuning the UCNPs excitation wavelength. This review focuses on recent advances in the development of NIR-initiated DDS, with emphasis on the use of photo-responsive compounds and polymeric materials conjugated onto UCNPs. The challenges that limit UCNPs clinical applications, alongside with the aforementioned techniques that have emerged to overcome these limitations, are highlighted.

  8. Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

    PubMed

    Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

    2016-02-01

    This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

  9. Ho3+-doped strontium-aluminium-bismuth-borate glasses for green light emission.

    PubMed

    Rajesh, D; Dhamodhara Naidu, M; Ratnakaram, Y C; Balakrishna, A

    2014-11-01

    Strontium-aluminium-bismuth-borate glasses (SAlBiB) doped with different concentrations of Ho(3+) were prepared using conventional melt quenching technique and their structural and optical properties investigated. X-ray diffraction and scanning electron microscopy analysis were used to study the structural properties. Optical properties were studied by measuring the optical absorption and visible luminescence spectra. The Judd-Ofelt (J-O) theory was applied to evaluate J-O intensity parameters, Ω(λ) (λ = 2, 4 and 6). Using J-O intensity parameters, radiative properties such as spontaneous transition probabilities (A(R)), branching ratios (β(R)) and radiative lifetimes (τ(R)) were determined. From the emission spectra, a strong green emission nearly at 549 nm corresponding to the transition, (5)S2 ((5)F4)→(5)I(8) was observed. Emission peak positions (λ(P)), effective bandwidths (Δλ(eff)) and stimulated emission cross-sections (σ(p)) were calculated for the observed emission transitions, (5)F3 →(5)I(8), (5)S2((5)F4)→(5)I(8) and (5)F5 →(5)I(8) of Ho(3+) in all the glass matrices. Chromaticity color coordinates were calculated using the emission spectra. The experimental results suggest that SAlBiB glass matrix with 1.5 mol% of Ho(3+) has better emission properties.

  10. Eu3+ ion doped sodium-lead borophosphate glasses for red light emission

    NASA Astrophysics Data System (ADS)

    Kiran, Nallamala

    2014-05-01

    Sodium-lead borophosphate glasses doped with different concentrations of Eu3+ ion are prepared by using the melt quenching technique to study their physical, XRD FTIR and luminescence properties to understand the lasing potentialities of these glasses. The XRD studies confirm the amorphous nature of the glasses. FTIR spectrum indicates the presence of BO3 and PO4 structural units. From the emission spectra, Judd-Ofelt (J-O) intensity parameters have been evaluated from the transition 5D0 → 7FJ (J = 2 and 4). The evaluated (J-O) intensity parameters have been used to calculate the radiative transition probabilities, luminescence branching ratio and radiative decay times. The intensity ratio (R) value due to 5D0 → 7F2/5D0 → 7F1 transition intensity of Eu3+ ions, increase with increasing concentrations suggesting higher asymmetry and covalent bonding character between rare earth ion and oxygen ligands. The chromaticity coordinates were calculated and analyzed with Commission International deI'Eclairage color diagram. The lifetimes of 5D0 metastable state for the samples with different concentrations were also measured and discussed. The predicted and experimental lifetimes for the 5D0 level in sodium lead borophosphate glasses were compared and discussed in detail.

  11. UV light induced red emission in Eu3+-doped zincborophosphate glasses

    NASA Astrophysics Data System (ADS)

    Hima Bindu, S.; Siva Raju, D.; Vinay Krishna, V.; Rajavardhana Rao, T.; Veerabrahmam, K.; Linga Raju, Ch.

    2016-12-01

    This paper reports the preparation of transparent zincborophosphate (ZBP) glasses doped with Eu3+ ions by the conventional melt quenching technique. The prepared glasses were characterized using powder XRD, FTIR, optical absorption, photoluminescence and decay curves. Judd-Ofelt (JO) intensity parameters calculated under various constraints using absorption and emission spectra. These JO intensity parameters have been used to predict the radiative properties such as radiative life time, branching ratios and stimulated emission cross section of the 5D0→7FJ (J = 0-4) transitions. Decay curves for the 5D0 level of Eu3+ ions shows single exponential for all concentrations. Luminescence properties of 5D0→7F2 transitions of Eu3+ions have revealed that the present ZBP:Eu3+ glasses have significant in optical applications at around 613 nm. An intense red luminescence has been observed due to 5D0→7F2 transition of Eu3+ ion in these glasses. From the CIE color coordinate diagram, it is observed that the present glass system is prominent material for red emission.

  12. Low-Temperature Preparation of Ag-Doped ZnO Nanowire Arrays, DFT Study, and Application to Light-Emitting Diode.

    PubMed

    Pauporté, Thierry; Lupan, Oleg; Zhang, Jie; Tugsuz, Tugba; Ciofini, Ilaria; Labat, Frédéric; Viana, Bruno

    2015-06-10

    Doping ZnO nanowires (NWs) by group IB elements is an important challenge for integrating nanostructures into functional devices with better and tuned performances. The growth of Ag-doped ZnO NWs by electrodeposition at 90 °C using a chloride bath and molecular oxygen precursor is reported. Ag acts as an electrocatalyst for the deposition and influences the nucleation and growth of the structures. The silver atomic concentration in the wires is controlled by the additive concentration in the deposition bath and a content up to 3.7 atomic % is reported. XRD analysis shows that the integration of silver enlarges the lattice parameters of ZnO. The optical measurements also show that the direct optical bandgap of ZnO is reduced by silver doping. The bandgap shift and lattice expansion are explained by first principle calculations using the density functional theory (DFT) on the silver impurity integration as an interstitial (Ag(i)) and as a substitute of zinc atom (Ag(Zn)) in the crystal lattice. They notably indicate that Ag(Zn) doping forms an impurity band because of Ag 4d and O 2p orbital interactions, shifting the Fermi level toward the valence band. At least, Ag-doped ZnO vertically aligned nanowire arrays have been epitaxially grown on GaN(001) substrate. The heterostructure has been inserted in a light emitting device. UV-blue light emission has been achieved with a low emission threshold of 5 V and a tunable red-shifted emission spectrum related to the bandgap reduction induced by silver doping of the ZnO emitter material.

  13. Source/Drain Engineering for High Performance Vertical MOSFET

    NASA Astrophysics Data System (ADS)

    Imamoto, Takuya; Endoh, Tetsuo

    In this paper, Source/Drain (S/i>/D) engineering for high performance (HP) Vertical MOSFET (V-MOSFET) in 3Xnm generation and its beyond is investigated, by using gradual S/i>/D profile while degradation of driving current (ION) due to the parasitic series resistance (Rpara) is minimized through two-dimensional device simulation taking into account for gate-induced-drain-leakage (GIDL). In general, it is significant to reduce spreading resistance in the case of conventional Planar MOSFET. Therefore, in this study, we focused and analyzed the abruptness of diffusion layer that is still importance parameter in V-MOSFET. First, for improving the basic device performance such as subthreshold swing (SS), ION, and Rpara, S/D engineering is investigated. The dependency of device performance on S/D abruptness (σS/D) for various Lightly Doped Drain Extension (LDD) abruptness (σLDD) is analyzed. In this study, Spacer Length (LSP) is defined as a function of σS/D. As σS/D becomes smaller and S/D becomes more abrupt, LSP becomes shorter. SS depends on the σS/D rather than the σLDD. ION has the peak value of 1750µA/µm at σS/D =2nm/dec. and σLDD=3nm/dec. when the silicon pillar diameter (D) is 30nm and the gate length (Lg) is 60nm. As σS/D becomes small, higher ION is obtained due to reduction of Rpara while SS is degraded. However, when σS/D becomes too small in the short channel devices (Lg =60nm and Lg =45nm), ION is degraded because the leakage current due to GIDL is increased and reaches IOFF limit of 100nA/µm. In addition, as σLDD becomes larger, larger ION is obtained in the case of Lg =100nm and Lg =60nm because channel length becomes shorter. On the other hand, in the case of Lg =45nm, as σLDD becomes larger, ION is degraded because short channel effect (SCE) becomes significant. Next, the dependency of the basic device performance on D is investigated. By slimming D from 30nm to 10nm, while SS is improved and approaches the ideal value of 60mV/Decade, ION

  14. Origin of Mechanoluminescence from Cu-Doped ZnS Particles Embedded in an Elastomer Film and Its Application in Flexible Electro-mechanoluminescent Lighting Devices.

    PubMed

    Shin, Seung Wook; Oh, Jeung Pyo; Hong, Chang Woo; Kim, Eun Mi; Woo, Jeong Ju; Heo, Gi-Seok; Kim, Jin Hyeok

    2016-01-20

    Mechanically driven light emission from particles embedded in elastomer films has recently attracted interest as a strong candidate for next-generation light sources on display devices because it is nondestructive, reproducible, real-time, environmentally friendly, and reliable. The origin of mechanoluminescence (ML) obtained from particles embedded in elastomer films have been proposed as the trapping of drifting charge carriers in the presence of a piezoelectric field. However, in this study, we propose a new origin of ML through the study of the microstructure of a Cu-doped ZnS particles embedded in an elastomer composite film with high brightness using transmission electron microscopy (TEM) to clearly demonstrate the origin of ML with respect to the microstructure of ML composite films. The TEM characterization of the ML composite film demonstrated that the Cu-doped ZnS particles were fully encapsulated by a 500 nm thick Al layer, which acts as an electron source for ML emission. Furthermore, we fabricated a flexible electro-mechanoluminescence (EML) device using a Cu-doped ZnS particles embedded in a flexible elastomer composite film. Our research results on a new emission mechanism for ML and its application in flexible light generating elastomer films represent an important step toward environmentally benign and ecofriendly flexible electro-mechanoluminescent lighting devices.

  15. Tungsten oxide doped N ,N'-di(naphthalen-1-yl)-N ,N'-diphenyl-benzidine as hole injection layer for high performance organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Wang, Fengxia; Qiao, Xianfeng; Xiong, Tao; Ma, Dongge

    2009-04-01

    By introducing tungsten oxide (WO3) doped N ,N'-di(naphthalen-1-yl)-N ,N'-diphenyl-benzidine (NPB) hole injection layer, the great improvement in device efficiency and the organic film morphology stability at high temperature were realized for organic light-emitting diodes (OLEDs). The detailed investigations on the improvement mechanism by optical, electric, and film morphology properties were presented. The experimental results clearly demonstrated that using WO3 doped NPB as the hole injection layer in OLEDs not only reduced the hole injection barrier and enhanced the transport property, leading to low operational voltage and high efficiency, but also improved organic film morphology stability, which should be related to the device stability. It could be seen that due to the utilization of WO3 doped NPB hole injection layer in NPB/tris (8-quinolinolato) aluminum (Alq3)-based device, the maximum efficiency reached 6.1 cd A-1 and 4.8 lm W-1, which were much higher than 4.5 cd A-1 and 1.1 lm W-1 of NPB/Alq3 device without hole injection layer. The device with WO3 doped NPB hole injection layer yet gave high efficiency of 6.1 cd A-1 (2.9 lm W-1) even though the device was fabricated at substrate temperature of 80 °C. These results adequately indicated that WO3 doped NPB was a promising hole injection layer for high efficiency and high stability OLEDs.

  16. N-Doped TiO2 Nanobelts with Coexposed (001) and (101) Facets and Their Highly Efficient Visible-Light-Driven Photocatalytic Hydrogen Production.

    PubMed

    Sun, Shuchao; Gao, Peng; Yang, Yurong; Yang, Piaoping; Chen, Yujin; Wang, Yanbo

    2016-07-20

    To narrow the band gap (3.2 eV) of TiO2 and extend its practical applicability under sunlight, the doping with nonmetal elements has been used to tune TiO2 electronic structure. However, the doping also brings new recombination centers among the photoinduced charge carriers, which results in a quantum efficiency loss accordingly. It has been proved that the {101} facets of anatase TiO2 are beneficial to generating and transmitting more reductive electrons to promote the H2-evolution in the photoreduction reaction, and the {001} facets exhibit a higher photoreactivity to accelerate the reaction involved of photogenerated hole. Thus, it was considered by us that using the surface heterojunction composed of both {001} and {101} facets may depress the disadvantage of N doping. Fortunately, we successfully synthesized anatase N-doped TiO2 nanobelts with a surface heterojunction of coexposed (101) and (001) facets. As expected, it realized the charge pairs' spatial separation and showed higher photocatalytic activity under a visible-light ray: a hydrogen generation rate of 670 μmol h(-1) g(-1) (much higher than others reported previously in literature of N-doped TiO2 nanobelts).

  17. Photoinactivation of Escherichia coli by sulfur-doped and nitrogen-fluorine-codoped TiO2 nanoparticles under solar simulated light and visible light irradiation.

    PubMed

    Pathakoti, Kavitha; Morrow, Shavonda; Han, Changseok; Pelaez, Miguel; He, Xiaojia; Dionysiou, Dionysios D; Hwang, Huey-Min

    2013-09-03

    Titanium dioxide (TiO2) is one of the most widely used photocatalysts for the degradation of organic contaminants in water and air. Visible light (VL) activated sulfur-doped TiO2 (S-TiO2) and nitrogen-fluorine-codoped TiO2 (N-F-TiO2) were synthesized by sol-gel methods and characterized. Their photoinactivation performance was tested against Escherichia coli under solar simulated light (SSL) and VL irradiation with comparison to commercially available TiO2. Undoped Degussa-Evonik P-25 (P-25) and Sigma-TiO2 showed the highest photocatalytic activity toward E. coli inactivation under SSL irradiation, while S-TiO2 showed a moderate toxicity. After VL irradiation, Sigma-TiO2 showed higher photoinactivation, whereas S-TiO2 and P-25 showed moderate toxicity. Oxidative stress to E. coli occurred via formation of hydroxyl radicals leading to lipid peroxidation as the primary mechanism of bacterial inactivation. Various other biological models, including human keratinocytes (HaCaT), zebrafish liver cells (ZFL), and zebrafish embryos were also used to study the toxicity of TiO2 NPs. In conclusion, N-F-TiO2 did not show any toxicity based on the assay results from all the biological models used in this study, whereas S-TiO2 was toxic to zebrafish embryos under all the test conditions. These findings also demonstrate that the tested TiO2 nanoparticles do not show any adverse effects in HaCaT and ZFL cells.

  18. One-pot synthesis of copper-doped graphitic carbon nitride nanosheet by heating Cu–melamine supramolecular network and its enhanced visible-light-driven photocatalysis

    SciTech Connect

    Gao, Junkuo; Wang, Jiangpeng; Qian, Xuefeng; Dong, Yingying; Xu, Hui; Song, Ruijing; Yan, Chenfeng; Zhu, Hangcheng; Zhong, Qiwei; and others

    2015-08-15

    Here we report a novel synthetic pathway for preparation of Cu-doped g-C{sub 3}N{sub 4} (Cu-g-C{sub 3}N{sub 4}) with nanosheet morphology by using a two dimensional Cu–melamine supramolecular network as both sacrificial template and precursor. The specific surface area of Cu-g-C{sub 3}N{sub 4} is 40.86 m{sup 2} g{sup −1}, which is more than 7 times larger than that of pure g-C{sub 3}N{sub 4}. Cu-g-C{sub 3}N{sub 4} showed strong optical absorption in the visible-light region and expanded the absorption to the near-infrared region. The uniform nanosheet morphology, higher surface area and strong visible-light absorption have enabled Cu-g-C{sub 3}N{sub 4} exhibiting enhanced visible light photocatalytic activity for the photo-degradation of methylene blue (MB). The results indicate that metal–melamine supramolecular network can be promising precursors for the one step preparation of efficient metal-doped g-C{sub 3}N{sub 4} photocatalysts. - Graphical abstract: Cu-doped g-C{sub 3}N{sub 4} (Cu-g-C{sub 3}N{sub 4}) with nanosheet morphology was fabricated via a simple one step preparation by using a two dimensional Cu–melamine supra-molecular network as both sacrificial template and precursor. - Highlights: • Cu-doped g-C{sub 3}N{sub 4} (Cu-g-C{sub 3}N{sub 4}) with nanosheet morphology was prepared. • Cu-g-C{sub 3}N{sub 4} showed strong optical absorption in the visible-light region. • Cu-g-C{sub 3}N{sub 4} exhibits enhanced visible light photocatalytic activity.

  19. Facile synthesis of aluminium doped zinc oxide-polyaniline hybrids for photoluminescence and enhanced visible-light assisted photo-degradation of organic contaminants

    NASA Astrophysics Data System (ADS)

    Mitra, Mousumi; Ghosh, Amrita; Mondal, Anup; Kargupta, Kajari; Ganguly, Saibal; Banerjee, Dipali

    2017-04-01

    The emergence of organic-inorganic photoactive materials has led to marked progress in the field of heterogeneous visible-light photocatalysis. Visible-light active aluminium doped zinc oxide-polyaniline (PAZ) hybrid was prepared employing in-situ oxidative polymerization of polyaniline (PANI) in the presence of aluminium doped zinc oxide (AlZnO) nanorods, synthesized via sol-gel route. The compositions, structural and optical properties of the synthesized hybrids were characterized. Among various samples, the 22 wt% aluminium doped zinc oxide-polyaniline (PAZ 3) hybrid show the best photocatalytic action for the degradation of methyl orange (MO) and rose bengal (RB) dyes under visible-light illumination, even after repeated use. The performance of the photocatalytic process was determined by the first order rate constant, 1.77 × 10-2 min-1 and 2.61 × 10-2 min-1 for MO and RB dyes, respectively. Scavenger test was used to determine the role of active species and accordingly a mechanism was proposed. Electrochemical impedance spectroscopy and linear scan voltammetry under dark and visible-light irradiation also established the visible-light activity of the PAZ hybrid due to decrease in the electron transfer resistance that resulted in an enhancement in photocurrent. The significant enhancement of photo degradation may be attributed to the efficiency of charge separation, induced by synergistic effect between an organic conductor PANI and an inorganic semiconductor AlZnO. Owing to its superior photo electrochemical performance and photocatalytic degradation, aluminium doped zinc oxide-polyaniline (PAZ) hybrid offers stable and efficient organic-inorganic hybrid hetero-structures in near future.

  20. Generation of airborne listeria from floor drains

    USDA-ARS?s Scientific Manuscript database

    Listeria monocytogenes can colonize floor drains in poultry processing and further processing facilities remaining even after cleaning and disinfection. Therefore, during wash down, workers exercise caution to prevent escape and transfer of drain microflora to food contact surfaces. The objective ...