scholarly journals Charge accumulation kinetics in multi-redox molecular catalysts immobilised on TiO2

2021 ◽  
Author(s):  
Carlota Bozal-Ginesta ◽  
Camilo A. Mesa ◽  
Annika Eisenschmidt ◽  
Laia Francàs ◽  
Ravi B. Shankar ◽  
...  
Keyword(s):  
Light Intensity ◽  
Charge Accumulation ◽  
Applied Bias ◽  
Accumulation Kinetics ◽  
Molecular Catalysts

Using transient spectroelectrochemical techniques, we investigate multiply reduced states of molecular catalysts on titania photoelectrodes as a function of the applied bias and the light intensity.

scholarly journals Charge Accumulation Kinetics in Multi-redox Molecular Catalysts Immobilised on TiO2

2020 ◽  
Author(s):  
Carlota Bozal-Ginesta ◽  
Camilo A. Mesa ◽  
Annika Eisenschmidt ◽  
Ravi Shankar ◽  
Laia Francàs ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Redox Potentials ◽  
Charge Accumulation ◽  
Excitation Light ◽  
Molecular Catalyst ◽  
Hole Scavenger ◽  
Accumulation Kinetics ◽  
Molecular Catalysts

Multi-redox catalysis requires the transfer of more than one charge carrier and is crucial for solar energy conversion into fuels and valuable chemicals. In photo(electro)chemical systems, however, the necessary accumulation of multiple, long-lived charges is challenged by recombination with their counterparts. Herein, we investigate charge accumulation in two model multi-redox molecular catalysts for proton and CO<sub>2</sub> reduction attached onto mesoporous TiO<sub>2</sub> electrodes. Transient absorption spectroscopy and spectroelectrochemical techniques have been employed to study the kinetics of photoinduced electron transfer from the TiO<sub>2</sub> to the molecular catalysts in acetonitrile, with triethanolamine as the hole scavenger. At high light intensities, we detect charge accumulation in the millisecond timescale in the form of multi-reduced species. The redox potentials of the catalysts and the capacity of TiO<sub>2</sub> to accumulate electrons play an essential role in the charge accumulation process at the molecular catalyst. Recombination of reduced species with valence band holes in TiO<sub>2</sub> is observed to be faster than microseconds, while electron transfer from multi-reduced species to the conduction band or the electrolyte occurs in the millisecond timescale. Finally, under light irradiation, we show how charge accumulation on the catalyst is regulated as a function of the applied bias and the excitation light intensity.

scholarly journals Charge Accumulation Kinetics in Multi-redox Molecular Catalysts Immobilised on TiO2

2020 ◽  
Author(s):  
Carlota Bozal-Ginesta ◽  
Camilo A. Mesa ◽  
Annika Eisenschmidt ◽  
Ravi Shankar ◽  
Laia Francàs ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Redox Potentials ◽  
Charge Accumulation ◽  
Excitation Light ◽  
Molecular Catalyst ◽  
Hole Scavenger ◽  
Accumulation Kinetics ◽  
Molecular Catalysts

Multi-redox catalysis requires the transfer of more than one charge carrier and is crucial for solar energy conversion into fuels and valuable chemicals. In photo(electro)chemical systems, however, the necessary accumulation of multiple, long-lived charges is challenged by recombination with their counterparts. Herein, we investigate charge accumulation in two model multi-redox molecular catalysts for proton and CO<sub>2</sub> reduction attached onto mesoporous TiO<sub>2</sub> electrodes. Transient absorption spectroscopy and spectroelectrochemical techniques have been employed to study the kinetics of photoinduced electron transfer from the TiO<sub>2</sub> to the molecular catalysts in acetonitrile, with triethanolamine as the hole scavenger. At high light intensities, we detect charge accumulation in the millisecond timescale in the form of multi-reduced species. The redox potentials of the catalysts and the capacity of TiO<sub>2</sub> to accumulate electrons play an essential role in the charge accumulation process at the molecular catalyst. Recombination of reduced species with valence band holes in TiO<sub>2</sub> is observed to be faster than microseconds, while electron transfer from multi-reduced species to the conduction band or the electrolyte occurs in the millisecond timescale. Finally, under light irradiation, we show how charge accumulation on the catalyst is regulated as a function of the applied bias and the excitation light intensity.

scholarly journals Stabilization of a molecular water oxidation catalyst on a dye−sensitized photoanode by a pyridyl anchor

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Yong Zhu ◽  
Degao Wang ◽  
Qing Huang ◽  
Jian Du ◽  
Licheng Sun ◽  
...  
Keyword(s):  
Water Splitting ◽  
Phosphonic Acid ◽  
Water Oxidation ◽  
Oxidation Catalyst ◽  
Molecular Water ◽  
Applied Bias ◽  
Surface Loading ◽  
Dye Sensitized ◽  
Monomeric Structure ◽  
Molecular Catalysts

Abstract Understanding and controlling the properties of water-splitting assemblies in dye-sensitized photoelectrosynthesis cells is a key to the exploitation of their properties. We demonstrate here that, following surface loading of a [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) chromophore on nanoparticle electrodes, addition of the molecular catalysts, Ru(bda)(L)2 (bda  =  2,2′-bipyridine-6,6′-dicarboxylate) with phosphonate or pyridyl sites for water oxidation, gives surfaces with a 5:1 chromophore to catalyst ratio. Addition of the surface-bound phosphonate derivatives with L = 4-pyridyl phosphonic acid or diethyl 3-(pyridin-4-yloxy)decyl-phosphonic acid, leads to well-defined surfaces but, following oxidation to Ru(III), they undergo facile, on-surface dimerization to give surface-bound, oxo-bridged dimers. The dimers have a diminished reactivity toward water oxidation compared to related monomers in solution. By contrast, immobilization of the Ru-bda catalyst on TiO2 with the 4,4′-dipyridyl anchoring ligand can maintain the monomeric structure of catalyst and gives relatively stable photoanodes with photocurrents that reach to 1.7 mA cm−2 with an optimized, applied bias photon-to-current efficiency of 1.5%.

Tailored Laser scanned photodiodes (LSP) for image recognition

2001 ◽  
Vol 664 ◽  
Author(s):  
M. Vieira ◽  
M. Fernandes ◽  
P. Louro ◽  
Y. Vygranenko ◽  
R. Schwarz ◽  
...  
Keyword(s):  
Light Intensity ◽  
Laser Beam ◽  
Spatial Resolution ◽  
Image Recognition ◽  
Signal Intensity ◽  
Charge Accumulation ◽  
Optical Gap ◽  
Imaging Detector ◽  
Carrier Collection ◽  
Mis Structures

ABSTRACTA tailored ZnO:Al/a-p-i-n SiC:H/Al configuration for the laser scanned photodiode (LSP) imaging detector is proposed. The LSP utilizes light modulated depletion layers as detector and a laser beam for readout. When highly resistive a-SiC:H doped layers are used its higher optical gap when compared with the active layer are responsible by charge accumulation at the illuminated interfaces which blocks the carrier collection under illumination. Those insulator-like layers act as MIS structures that prevent excess signal charge from blooming to the nearby dark regions avoiding the image smearing.The optical-to-electrical transfer characteristics show reciprocity between light intensity and image signal intensity only limited by the doped layers composition. Data reveal that the sensitivity, the responsivity and the spatial resolution are limited by the cell configuration while the linearity depends on the light source flux used to map the image onto the sensor. By using tailored SiC:H/Si:H/SiC:H p-i-n heterostructures an increase in the image signal optimized to the blue is achieved with a responsivity of 0.2 mW/cm2 and a spatial resolution of 20 µm.

Fast Diamond Photoconductors

1993 ◽  
Vol 302 ◽  
Author(s):  
T. Pochet ◽  
B. Brullot ◽  
R. Galli ◽  
C. Rubbelynck
Keyword(s):  
Light Intensity ◽  
Laser Pulse ◽  
Gamma Ray ◽  
Applied Bias ◽  
Preliminary Results ◽  
Detector Sensitivity

ABSTRACTPreliminary results on the response of type Ib and IIa diamond photodetectors to fast laser pulse exposures at 265 and 530 nm are presented. The influence of the applied bias, the laser wavelengths and the light intensity on the detector sensitivity is studied. Also, recent measurements with 1.25 MeV gamma ray pulses are reported.

Surface state controlled ultrahigh selectivity and sensitivity for UV photodetectors based on individual SnO2 nanowires

2016 ◽  
Vol 4 (36) ◽  
pp. 8399-8406 ◽  
Author(s):  
Haiping Shi ◽  
Baochang Cheng ◽  
Qiangsheng Cai ◽  
Xiaohui Su ◽  
Yanhe Xiao ◽  
...  
Keyword(s):  
Light Intensity ◽  
Bias Voltage ◽  
Surface State ◽  
High Performance ◽  
Surface States ◽  
Applied Bias ◽  
Applied Bias Voltage ◽  
Uv Photodetectors ◽  
Sno2 Nanowires

Surface states are utilized for the development of high-performance photodetectors based on individual SnO2 nanowires. Their photodetectivity strongly depends on externally applied bias voltage and illuminated light intensity.

Study of charge accumulation kinetics in MOS structures with intrinsic anodic oxide on InSb by measuring transient photocurrents

1985 ◽  
Vol 90 (1) ◽  
pp. 393-400
Author(s):  
N. A. Avdeev ◽  
Yu. E. Gabdin ◽  
V. A. Gurtov ◽  
S. N. Kuznetsov
Keyword(s):  
Anodic Oxide ◽  
Charge Accumulation ◽  
Accumulation Kinetics ◽  
Mos Structures

Time variation of GaN photoelectrochemical reactions affected by light intensity and applied bias

2010 ◽  
Vol 7 (7-8) ◽  
pp. 2221-2223 ◽  
Author(s):  
Kayo Koike ◽  
Keiichi Sato ◽  
Katsushi Fujii ◽  
Takenari Goto ◽  
Takafumi Yao
Keyword(s):  
Light Intensity ◽  
Time Variation ◽  
Applied Bias

SPIN TRANSPORT IN MULTIPLY CONNECTED FRACTAL CONDUCTORS

SPIN ◽  
2014 ◽  
Vol 04 (03) ◽  
pp. 1450007 ◽  
Author(s):  
BO-RAY LEE ◽  
CHING-RAY CHANG ◽  
IVO KLIK
Keyword(s):  
Green Function ◽  
Spin Transport ◽  
Quantum Wires ◽  
Tight Binding ◽  
Spin Accumulation ◽  
Charge Accumulation ◽  
Applied Bias ◽  
Multiply Connected ◽  
Resonant Modes ◽  
High Bias

We consider spin and charge transport in a Sierpinski planar carpet; the interest here is its unique geometry. We analyze the fractal conductor as a combination of multiply connected quantum wires, and we observe the evolution of the transmission envelope in different fractal generations. For a fractal conductor dominated by resonant modes the transmission is characterized by strong fluctuations and conduction gaps. We show that charge and spin transport have different responses both to the presence of defects and to applied bias. At a high bias, or in a high-order fractal generation, spin accumulation is separated from charge accumulation because the larger drift velocity needs a longer polarization length, and the sample may turn into an insulator by the action of the defects. Our results are calculated numerically using the Keldysh Green function within the tight-binding framework.

Fine structure of the retina of the giant scallop, Placopecten magellanicus

1984 ◽  
Vol 42 ◽  
pp. 312-313
Author(s):  
C.V.L. Powell
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Light Intensity ◽  
Scanning Electron Microscope ◽  
Eye Development ◽  
Preliminary Observation ◽  
Columnar Epithelium ◽  
Placopecten Magellanicus ◽  
Environmental Light ◽  
Scanning Electron

The overall fine structure of the eye in Placopecten is similar to that of other scallops. The optic tentacle consists of an outer columnar epithelium which is modified into a pigmented iris and a cornea (Fig. 1). This capsule encloses the cellular lens, retina, reflecting argentea and the pigmented tapetum. The retina is divided into two parts (Fig. 2). The distal retina functions in the detection of movement and the proximal retina monitors environmental light intensity. The purpose of the present study is to describe the ultrastructure of the retina as a preliminary observation on eye development. This is also the first known presentation of scanning electron microscope studies of the eye of the scallop.

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