Enhanced visible-light absorption of mesoporous TiO2 by co-doping with transition-metal/nitrogen ions

2013 ◽  
Vol 1547 ◽  
pp. 115-119 ◽  
Author(s):  
J. E. Mathis ◽  
Z. Bi ◽  
C. A. Bridges ◽  
M. K. Kidder ◽  
M. P. Paranthaman
Keyword(s):  
Transition Metals ◽  
Band Gap ◽  
Near Infrared ◽  
Solar Spectrum ◽  
Visible Spectrum ◽  
Solar Irradiation ◽  
Major Drawback ◽  
Co Doping ◽  
Energy Applications ◽  
Sufficient Energy

ABSTRACTTitanium (IV) oxide, TiO2, has been the object of intense scrutiny for energy applications. TiO2 is inexpensive, non-toxic, and has excellent corrosion resistance when exposed to electrolytes. A major drawback preventing the widespread use TiO2 for photolysis is its relatively large band gap of ∼3eV. Only light with wavelengths shorter than 400 nm, which is in the ultraviolet portion of the spectrum, has sufficient energy to be absorbed. Less than 14 percent of the solar irradiation reaching the earth’s surface has energy exceeding this band gap. Adding dopants such as transition metals has long been used to reduce the gap and increase photocatalytic activity by accessing the visible part of the solar spectrum. The degree to which the band gap is reduced using transition metals depends in part on the overlap of the d-orbitals of the transition metals with the oxygen p-orbitals. Therefore, doping with anions such as nitrogen to modify the cation-anion orbital overlap is another approach to reduce the gap. Recent studies suggest that using a combination of transition metals and nitrogen as dopants is more effective at introducing intermediate states within the band gap, effectively narrowing it. Here we report the synthesis of mesoporous TiO2 spheres, co-doped with transition metals and nitrogen that exhibit a nearly flat absorbance response across the visible spectrum extending into the near infrared.

scholarly journals Synergistic Effects in a ZnO Powder-Based Coating Sequentially Irradiated with Protons, Electrons, and Solar Spectrum Quanta

Symmetry ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1021
Author(s):  
Mikhail M. Mikhailov ◽  
Semyon A. Yuryev ◽  
Alexey N. Lapin ◽  
Vadim V. Karanskiy
Keyword(s):  
Zinc Oxide ◽  
Absorption Coefficient ◽  
Near Infrared ◽  
Synergistic Effects ◽  
High Vacuum ◽  
Visible Region ◽  
Solar Spectrum ◽  
Complete Recovery ◽  
Solar Irradiation ◽  
Integral Absorption

The authors investigated the changes in diffuse reflectance spectra (ρλ) within 0.32–2.1 μm and integral absorption coefficient (as) of solar irradiation for a zinc oxide powder-based coating. The latter was consequently irradiated with protons (E = 3 keV, F ≤ 1 × 1016 cm−2), solar spectrum quanta (5 eq. of solar irradiation, 1 h), electrons (E = 30 keV, F = 1 × 1016 cm−2), and—repetitively—solar spectrum quanta (5 eq. of solar irradiation, 1 h). Following the irradiation procedure, the decrease in absorption coefficient varied from 0.044 to 0.036 and from 0.062 to 0.04, respectively. Additionally, it was shown that the solar spectrum quanta did not significantly affect the coating pre-irradiated with protons or electrons and did not change the value of induced absorption in the visible region (the latter being caused by the absorption of intrinsic point defects of the zinc oxide crystal lattice). The absorption coefficient degradation decreased under solar spectrum quanta irradiation, which was determined by the decrease in the concentration of free electrons that absorbed in the near-infrared (near-IR) region. ρλ spectra were measured in high vacuum in situ. A post-irradiation transfer of a coating into the atmosphere leads not only to the complete recovery of its reflectance, but also to partial translucence in comparison with the non-irradiated state.

scholarly journals Characterization and Evaluation of the Efficiency of TiO2/Zinc Phthalocyanine Nanocomposites as Photocatalysts for Wastewater Treatment Using Solar Irradiation

2008 ◽  
Vol 2008 ◽  
pp. 1-12 ◽  
Author(s):  
Antonio E. H. Machado ◽  
Marcela D. França ◽  
Valdemir Velani ◽  
Gabriel A. Magnino ◽  
Hosana M. M. Velani ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Diffuse Reflectance ◽  
Near Infrared ◽  
Visible Spectrum ◽  
Zinc Phthalocyanine ◽  
Solar Irradiation ◽  
Absorption Bands ◽  
Intense Absorption ◽  
Spectrum Region

This work reports the characterization of composites prepared by the association between zinc phthalocyanine (ZnPc) and titanium dioxide. These composites are better photocatalysts for wastewater decontamination mediated by solar radiation than pureTiO2, performance that remains even when reused. The UV-Vis diffuse reflectance absorption spectra show for these composites two intense absorption bands. The first covers the ultraviolet and part of the visible spectrum region until 460 nm (2.7 eV), whereas the second, nonstructured, goes from 475 nm until the near infrared with an absorption peak at 683 nm attributed to the Q band of ZnPc. The production of additionale−/h+pairs by these aggregates when photoexcited, their capability to act as charge carrier, the thickness and regularity of their distribution on theTiO2surface seem to be important parameters for the performance observed for these composites.

Advances and significance of solar reflectors in solar energy technology in Pakistan

2018 ◽  
Vol 29 (4) ◽  
pp. 435-455 ◽  
Author(s):  
Sophia Akhtar ◽  
M Khurram Hashmi ◽  
Ishaq Ahmad ◽  
Rizwan Raza
Keyword(s):  
Solar Energy ◽  
Solar Spectrum ◽  
Base Material ◽  
Protective Layer ◽  
Solar Irradiation ◽  
Energy Crisis ◽  
Silver Coating ◽  
Energy Technology ◽  
Solar Panels ◽  
Energy Applications

Being located in the Sun Belt, Pakistan is rich in sunlight and receives a high mean irradiation. This condition is ideal for harnessing Sun’s power for solar energy applications by using solar reflectors. In spite of possessing such a rich solar irradiation area, Pakistan is facing energy crisis because most of the energy resources are still unexploited. This paper discusses the energy crisis of Pakistan and provides the solution by putting efforts into solar energy technology, as well as devising innovative ways to incorporate solar reflectors into a solar panel and get more power generation out of it by a diminutive modification. Reflectors are used in the solar technology to concentrate the sunlight onto the solar panels. They employ glass as a base material with a silver coating and a protective layer over it. They elevate the energy input of solar panels as the whole solar spectrum is reflected on them. Materials with more reflective properties are needed to be used to increase the reflectivity and efficiency of solar reflectors. In Pakistan, no significant work is done till now towards the development of solar reflectors. If solar reflectors are used with the solar panels, then their efficiency as well as production from the solar panels will be maximized.

scholarly journals Band Gap Reduction in Ferroelectric BaTiO3 Through Heterovalent Cu-Te Co-Doping for Visible-Light Photocatalysis

2021 ◽  
Vol 9 ◽  
Author(s):  
Rohit Kumar Rohj ◽  
Akmal Hossain ◽  
Priya Mahadevan ◽  
D. D. Sarma
Keyword(s):  
Band Gap ◽  
Ground State ◽  
Density Functional ◽  
Dopant Concentration ◽  
Ferroelectric Properties ◽  
Solar Spectrum ◽  
Visible Light Photocatalysis ◽  
Functional Theory ◽  
Co Doping ◽  
Photovoltaic Materials

It is believed that ferroelectrics may serve as efficient photocatalysts as well as photovoltaic materials but for their large bandgaps which does not allow them to absorb a large part of the solar spectrum. We have explored theoretically within ab-initio density functional theory-based calculations, the efficacy of Cu and Te to co-dope BaTiO3 in reducing its bandgap while retaining its ferroelectric properties. Examining a dopant concentration of 11%, we find an insulating ground state being realized with a band gap reduction of 0.42 eV from the value for undoped BaTiO3 for some doping configurations. Ferroelectric distortions are found to survive even in the presence of doping suggesting possible applications in photocatalysis as well as photovoltaics.

An Infrared Microscope for Use on a Focused Ion Beam for Circuit Edit and Backside Edit Applications

2015 ◽  
Author(s):  
Alexander Richards ◽  
Matthew Weschler ◽  
Michael Durller
Keyword(s):  
Focused Ion Beam ◽  
Near Infrared ◽  
Ion Beam ◽  
Visible Spectrum ◽  
Camera System ◽  
Buried Structures ◽  
Ir Camera ◽  
Area Of Interest ◽  
Near Ultraviolet ◽  
Infrared Microscope

Abstract To help solve the navigational problem, i.e., being able to successfully locate a circuit for probing or editing without destroying chip functionality, a near-infrared (NIR), near-ultraviolet (NUV), and visible spectrum camera system was developed that attaches to most focused ion beam (FIB) or scanning electron microscope vacuum chambers. This paper reviews the details of the design and implementation of the NIR/NUV camera system, as instantiated upon the FEI FIB 200, with a particular focus on its use for the visualization of buried structures, and also for non-destructive real time area of interest location and end point detection. It specifically considers the use of the micro-optical camera system for its benefit in assisting with frontside and backside circuit edit, as well as other typical FIB milling activities. The quality of the image obtained by the IR camera rivals or exceeds traditional optical based imaging microscopy techniques.

Optical Properties and Zinc Nitride Thin Films Prepared Using Magnetron Reactive Sputtering

2014 ◽  
Vol 940 ◽  
pp. 11-15
Author(s):  
Jun Qin Feng ◽  
Jun Fang Chen
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Near Infrared ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Sem Images ◽  
Fluorescence Emission Spectra ◽  
Glass Substrates ◽  
Zinc Nitride ◽  
Direct Band

Zinc nitride films were deposited by ion sources-assisted magnetron sputtering with the use of Zn target (99.99% purity) on 7059 glass substrates. The films were characterized by XRD, SEM and EDS, the results of which show that the polycrystalline zinc nitride thin film can be grown on the glass substrates, the EDS spectrum confirmed the chemical composition of the films and the SEM images revealed that the zinc nitride thin films have a dense structure. Ultraviolet-visible-near infrared spectrophotometer was used to study the transmittance behaviors of zinc nitride thin films, which calculated the optical band gap by Davis Mott model. The results of the fluorescence emission spectra show the zinc nitride would be a direct band gap semiconductor material.

Electronic structure engineering of tin telluride through co-doping of bismuth and indium for high performance thermoelectrics: a synergistic effect leading to a record high room temperature ZT in tin telluride

2019 ◽  
Vol 7 (16) ◽  
pp. 4817-4821 ◽  
Author(s):  
U. Sandhya Shenoy ◽  
D. Krishna Bhat
Keyword(s):  
Electronic Structure ◽  
Synergistic Effect ◽  
Band Gap ◽  
High Performance ◽  
Room Temperature ◽  
Band Offset ◽  
Valence Band Offset ◽  
Co Doping ◽  
Tin Telluride ◽  
Structure Engineering

Resonance states due to Bi and In co-doping, band gap enlargement, and a reduced valence-band offset in SnTe lead to a record high room-temperature ZT.

scholarly journals Spectroscopic detection of forest diseases: a review (1970–2020)

2021 ◽  
Author(s):  
Lorenzo Cotrozzi
Keyword(s):  
Early Detection ◽  
Optical Sensors ◽  
Near Infrared ◽  
Sustainable Forest Management ◽  
Visible Spectrum ◽  
Cost Effective ◽  
Infrared Region ◽  
Forest Disturbances ◽  
Effective Manner ◽  
Forest Diseases

AbstractSustainable forest management is essential to confront the detrimental impacts of diseases on forest ecosystems. This review highlights the potential of vegetation spectroscopy in improving the feasibility of assessing forest disturbances induced by diseases in a timely and cost-effective manner. The basic concepts of vegetation spectroscopy and its application in phytopathology are first outlined then the literature on the topic is discussed. Using several optical sensors from leaf to landscape-level, a number of forest diseases characterized by variable pathogenic processes have been detected, identified and quantified in many country sites worldwide. Overall, these reviewed studies have pointed out the green and red regions of the visible spectrum, the red-edge and the early near-infrared as the spectral regions most sensitive to the disease development as they are mostly related to chlorophyll changes and symptom development. Late disease conditions particularly affect the shortwave-infrared region, mostly related to water content. This review also highlights some major issues to be addressed such as the need to explore other major forest diseases and geographic areas, to further develop hyperspectral sensors for early detection and discrimination of forest disturbances, to improve devices for remote sensing, to implement long-term monitoring, and to advance algorithms for exploitation of spectral data. Achieving of these goals will enhance the capability of vegetation spectroscopy in early detection of forest stress and in managing forest diseases.

scholarly journals Preparation of Ti-Nb-Fe-O Nanotubes on Ti10NbxFe Alloy and the Application for Photocatalytic Degradation under Solar Irradiation

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 327
Author(s):  
Yujie Zhao ◽  
Qiquan Li ◽  
Yan Li
Keyword(s):  
Photocatalytic Degradation ◽  
Mixed Oxide ◽  
Tio2 Nanotubes ◽  
Degradation Rate ◽  
Solar Irradiation ◽  
Methylene Blue Degradation ◽  
Co Doping ◽  
Secondary Pollution ◽  
The Rich ◽  
Thick Layers

Highly oriented and self-ordered titanium-niobium-iron mixed oxide nanotubes were synthesized by anodizing Ti10NbxFe alloys in ethylene glycol electrolytes containing NH4F and water at 20 °C. The nanostructure morphologies were found to depend closely on the nature of the alloy substrates. The results demonstrate the possibility of growing mixed oxide nanotubes possessing several-micrometer-thick layers by a simple and straightforward electrochemical route. The methylene blue degradation rate of fabricated Ti-Nb-Fe-O nanotubes increased by 33% compared to TiO2 nanotubes and TiO2 nanoparticle films under solar irradiation. The combination of the gully-like morphology and the rich defects introduced by Nb and Fe co-doping in Ti-Nb-Fe-O mixed nanotube oxides was demonstrated to be beneficial for enhanced photocatalytic degradation performance. Ti-Nb-Fe-O nanotubes can achieve effective photodegradation without secondary pollution with more reusability than powder photocatalysts.

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