Download or read book Ultrafast Charge Carrier Dynamics in Bare and Surface modified Semiconductor Nanoparticles written by Jameel Abdul-Hadi Hasan and published by . This book was released on 2015 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: Charge-carrier relaxation dynamics in semiconductor nanoparticles has been in the forefront of research for last three decades both for their fundamental nature as well as for applications in light-harvesting, luminescent labels, light-emitting diodes and nonlinear optics. Significant research has focused on II-VI semiconductors with emphasis on CdS and CdSe that are toxic. On the other hand, ZnO and TiO2 semiconductor nanoparticles are less toxic and have enormous applications in photo-catalysis, water splitting, solar cells and optical sensors. However, the investigations of charge-carrier dynamics in these semiconductor nanomaterials compared to II-VI semiconductor quantum dots are quite limited. The knowledge of charge-carrier relaxation is essential to realize their optical applications. In this dissertation, efforts were made to probe ultrafast charge-carrier dynamics in bare ZnO and surface-modified TiO2 nanoparticles with combined femtosecond fluorescence upconversion and transient absorption measurements. Quantum-sized ZnO semiconductor nanoparticles show two luminescence bands corresponding to band-edge and trap-state luminescence where the dynamics of band-edge luminescence was not well understood. In this dissertation, studies were carried out to probe the ultrafast band-edge luminescence dynamics in bare ZnO nanoparticles as a function of size. The measurements have shown interesting role of rate of trapping in the band-edge luminescence dynamics and conclusively shown that trapping dynamics dominates the charge-carrier relaxation. Along similar lines, ultrafast interfacial charge-transfer emission was monitored in small molecule-modified TiO2 nanoparticles and have shown that small molecules create inter band-gap charge-transfer excitons that delocalize relatively fast into the conduction band of TiO2 leading to efficient charge separation. In this study, results revealed that increasing the strength of donor leads to better charge separation. Ultrafast measurements on chromophore-surface modified TiO2 nanoparticles have shown the role of localized charge-transfer excitons in charge separation and their use in dye solar cells. The results have shed light on heterogeneous interfacial charge-carrier relaxation dynamics in dye functionalized semiconductor nanoparticles. Finally, interesting trap-state luminescence of ZnO nanoparticles was used to develop turn-on luminescent dissolved oxygen (DO) sensors. Further, the sensitivity of ZnO nanoparticles towards DO was improved by preparing ZnO/graphene oxide nanocomposites that have shown additional ratiometric sensing capabilities for DO.
Download or read book ULTRAFAST CHARGE CARRIER DYNAMICS IN AU SEMICONDUCTOR NANOHETEROSTRUCTURES written by Scott Lambright and published by . This book was released on 2014 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Charge Carrier Dynamics of Bare and Dye sensitized Cerium Oxide Nanoparticles written by Jennifer Marie Empey and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The global need for clean renewable fuels has led to a high degree of interest in using photocatalytic processes that can form useful fuels. Semiconducting metal oxide materials have been extensively studied in this field due to their ability to generate highly reactive charge carriers upon photoexcitation, nontoxicity, and inexpensive fabrication. CeO2 has recently garnered interest as a photocatalytic material due to its redox mutability and relative abundance. In order to understand and improve the behavior of CeO2 as a photocatalyst, a thorough investigation into the dynamics of photoexcited charge carriers is needed. Herein, transient absorption spectroscopy was used to study the lifetime of photogenerated electrons and holes within CeO2 nanoparticles with varying diameters and crystalline domain sizes. Through tuning the size, the surface-to-bulk ratio is altered, allowing for a finer study of the surface and bulk hole dynamics in the nanoparticles. Through hole scavenging experiments, spectral assignments of surface and bulk holes were made and the behavior of these carriers vs electron small polarons (self-trapped electrons) was compared. The faster decay dynamics of ESPs in comparison with hole dynamics, both bulk and surface, reveals that the latter charge carrier is able to migrate away from its geminate partner and likely trap elsewhere within the particle. This observation suggests CeO2 nanoparticles should be considered photocatalysts for oxidation half reactions in which holes are employed. The surface holes were found to decay slower than the bulk holes, indicating that the latter trap/recombine more quickly. This long-lived decay for surface holes shows promise for the use of CeO2 as a photocatalytic oxidant. Signals from both holes and electrons small polarons decay slower in larger nanoparticles comprised of larger crystalline domains. This observation suggests the larger distance the electron small polaron must migrate or “hop” to within CeO2 aids in charge separation, allowing carriers within the larger nanoparticles to live longer. The disparate lifetimes for holes and electron small polarons in large and small nanoparticles suggest larger nanoparticles with larger crystalline domains are more useful as a photocatalyst despite the lower surface area in comparison to smaller nanoparticles. To further probe the surface states in CeO2, dye-sensitization experiments were carried out using coumarin 343, a visible light absorbing dye. By probing the transient absorption decay dynamics probed in the mid-IR and visible/near IR, electron injection and back-electron transfer dynamics of carriers introduced to CeO2 surface states were probed. Excitation of coumarin 343 bound to the surface of CeO2 using 430 nm light results in the formation of an oxidized dye signal in ≤300 fs, indicating CeO2 nanoparticles can support rapid electron injection. Additionally, excitation of C-343 bound CeO2 results in the formation of a measurable mid-infrared transient absorption signal not observed upon photoexcitation of bare CeO2 with UV light. The signal is assigned to an electron injected into a distribution of trap states made from Ce 5d orbitals, revealing the dissimilar nature of carriers promoted to the Ce 5d and Ce 4f states. To the best of our knowledge, the transient dynamics of electrons occupying the Ce 5d states have not previously been probed due to the high photonic energy needed to access these states. This result demonstrates a strategy for accessing Ce 5d states, which would not be easily attainable through excitation of bare CeO2 nanoparticles, as well as a method for injecting charge carriers into CeO2 using visible light. The decay of the mid-IR signal does not match the decay of the oxidized dye signal, indicating the injected electron first relaxes to a deeper set of trap states or to the Ce 4f states prior to back-electron transfer to oxidized coumarin 343. Pump wavelength dependent transient absorption and mid-IR transient experiments indicate that the back-electron transfer is limited by trapping distances of injected electrons from the surface bound oxidized dye.
Download or read book Charge Carrier Dynamics of Quantum Confined Semiconductor Nanoparticles Analyzed Via Transient Absorption Spectroscopy written by Arthur Joseph Thibert (III) and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The slower kinetics observed for the TBA2Ti4O9 nanosheets originates either from the presence of deeper trap sites on the sheets vs. the nanoparticles, more trap sites, or from more effective electron-hole separation because of the micrometer dimensions of the 2D lattice. Appendix II, depicts the visible solar spectrum at sea level detailing the percentage of photons and energy that exist within certain wavelength ranges.
Download or read book Ultrafast Carrier Dynamics in Semiconductor Nanostructures written by Markus Betz and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book 4D Electron Microscopy written by Ahmed H. Zewail and published by World Scientific. This book was released on 2010 with total page 359 pages. Available in PDF, EPUB and Kindle. Book excerpt: Structural phase transitions, mechanical deformations, and the embryonic stages of melting and crystallization are examples of phenomena that can now be imaged in unprecedented structural detail with high spatial resolution, and ten orders of magnitude as fast as hitherto. No monograph in existence attempts to cover the revolutionary dimensions that EM in its various modes of operation nowadays makes possible. The authors of this book chart these developments, and also compare the merits of coherent electron waves with those of synchrotron radiation. They judge it prudent to recall some important basic procedural and theoretical aspects of imaging and diffraction so that the reader may better comprehend the significance of the new vistas and applications now afoot. This book is not a vade mecum - numerous other texts are available for the practitioner for that purpose.
Download or read book Interface Effects on Charge Carrier Dynamics and Optical Gain in Ultrasmall Semiconductor Nanocrystals written by Patrick Brosseau and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this thesis, ultrafast pump-probe spectroscopy is used to investigate the effect ofinterfaces on charge carrier dynamics and optical gain in CdSe nanocrystals (NCs), CdSe/ZnS core/shell NCs and ultrasmall CdSe NCs. A narrow bandwidth photo-induced absorption (PA) feature has been identified as evidence of surface trapping in pump-probe transients in CdSe nanocrystals. Capping a CdSe NC with a ZnS shell diminishes this surface trapping signal by passivating the surface. However, both CdSe and CdSe/ZnS NCs also demonstrate a second, broad PA shelf upon excitation with an intense pump pulse. This PA shelf is expected to arise from charges trapped either at the surface of CdSe NCs or at the interface between CdSe andZnS in core/shell samples. Ultrasmall CdSe nanocrystals, with a diameter less than 2.5 nm, exhibit photoluminescence from both core and surface states. Pump-probe experiments show that the broad PA shelf is significantly more intense in ultrasmall nanocrystals. Gain measurements show that the gain threshold does not change significantly between nanocrystal diameters of 5.6 nm and 2.7 nm. However, gain is blocked in ultrasmall 2.2 nm nanocrystals due to intense photo-induced absorption. This is attributed to alarger surface to ratio in ultrasmall nanocrystals." --
Download or read book Ultrafast Carrier Dynamics in Organic inorganic Semiconductor Nanostructures written by Chaw Keong Yong and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Halide Perovskites written by Tze-Chien Sum and published by John Wiley & Sons. This book was released on 2019-03-25 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: Real insight from leading experts in the field into the causes of the unique photovoltaic performance of perovskite solar cells, describing the fundamentals of perovskite materials and device architectures. The authors cover materials research and development, device fabrication and engineering methodologies, as well as current knowledge extending beyond perovskite photovoltaics, such as the novel spin physics and multiferroic properties of this family of materials. Aimed at a better and clearer understanding of the latest developments in the hybrid perovskite field, this is a must-have for material scientists, chemists, physicists and engineers entering or already working in this booming field.
Download or read book Electrochemical Surface Science Basics and Applications written by Gaetano Granozzi and published by MDPI. This book was released on 2019-10-07 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrochemical surface science (EC-SS) is the natural advancement of traditional surface science (where gas–vacuum/solid interfaces are studied) to liquid (solution)/electrified solid interfaces. Such a merging between two different disciplines—i.e., surface science (SS) and electrochemistry—officially advanced ca. three decades ago. The main characteristic of EC-SS versus electrochemistry is the reductionist approach undertaken, inherited from SS and aiming to understand the microscopic processes occurring at electrodes on the atomic level. A few of the exemplary keystone tools of EC-SS include EC-scanning probe microscopies, operando and in situ spectroscopies and electron microscopies, and differential EC mass spectrometry (DEMS). EC-SS indirectly (and often unconsciously) receives a great boost from the requirement for rational design of energy conversion and storage devices for the next generation of energetic landscapes. As a matter of fact, the number of material science groups deeply involved in such a challenging field has tremendously expanded and, within such a panorama, EC and SS investigations are intimately combined in a huge number of papers. The aim of this Special Issue is to offer an open access forum where researchers in the field of electrochemistry, surface science, and materials science could outline the great advances that can be reached by exploiting EC-SS approaches. Papers addressing both the basic science and more applied issues in the field of EC-SS and energy conversion and storage materials have been published in this Special Issue.
Download or read book Semiconductor Nanomaterials written by Challa S. S. R. Kumar and published by John Wiley & Sons. This book was released on 2010-04-05 with total page 499 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book series Nanomaterials for the Life Sciences, provides an in-depth overview of all nanomaterial types and their uses in the life sciences. Each volume is dedicated to a specific material class and covers fundamentals, synthesis and characterization strategies, structure-property relationships and biomedical applications. The series brings nanomaterials to the Life Scientists and life science to the Materials Scientists so that synergies are seen and developed to the fullest. Written by international experts of various facets of this exciting field of research, the series is aimed at scientists of the following disciplines: biology, chemistry, materials science, physics, bioengineering, and medicine, together with cell biology, biomedical engineering, pharmaceutical chemistry, and toxicology, both in academia and fundamental research as well as in pharmaceutical companies. VOLUME 6 - Semiconductor Nanomaterials
Download or read book Nano Hetero Structures for Chemical Sensing Opportunities and Challenges written by Sheikh A. Akbar and published by Frontiers Media SA. This book was released on 2020-01-21 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Semiconductor Nanowires written by J Arbiol and published by Elsevier. This book was released on 2015-03-31 with total page 573 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor nanowires promise to provide the building blocks for a new generation of nanoscale electronic and optoelectronic devices. Semiconductor Nanowires: Materials, Synthesis, Characterization and Applications covers advanced materials for nanowires, the growth and synthesis of semiconductor nanowires—including methods such as solution growth, MOVPE, MBE, and self-organization. Characterizing the properties of semiconductor nanowires is covered in chapters describing studies using TEM, SPM, and Raman scattering. Applications of semiconductor nanowires are discussed in chapters focusing on solar cells, battery electrodes, sensors, optoelectronics and biology. - Explores a selection of advanced materials for semiconductor nanowires - Outlines key techniques for the property assessment and characterization of semiconductor nanowires - Covers a broad range of applications across a number of fields
Download or read book 2000 International Chemical Congress of Pacific Basin Societies written by and published by . This book was released on 2000 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Level Control at Hybrid Inorganic Organic Semiconductor Interfaces written by Raphael Schlesinger and published by Springer. This book was released on 2016-11-21 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work investigates the energy-level alignment of hybrid inorganic/organic systems (HIOS) comprising ZnO as the major inorganic semiconductor. In addition to offering essential insights, the thesis demonstrates HIOS energy-level alignment tuning within an unprecedented energy range. (Sub)monolayers of organic molecular donors and acceptors are introduced as an interlayer to modify HIOS interface-energy levels. By studying numerous HIOS with varying properties, the author derives generally valid systematic insights into the fundamental processes at work. In addition to molecular pinning levels, he identifies adsorption-induced band bending and gap-state density of states as playing a crucial role in the interlayer-modified energy-level alignment, thus laying the foundation for rationally controlling HIOS interface electronic properties. The thesis also presents quantitative descriptions of many aspects of the processes, opening the door for innovative HIOS interfaces and for future applications of ZnO in electronic devices.
Download or read book Electronic States and Optical Transitions in Solids written by Giuseppe Franco Bassani and published by Pergamon. This book was released on 1975 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photoelectrochemical Hydrogen Production written by Roel van de Krol and published by Springer Science & Business Media. This book was released on 2011-11-09 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photoelectrochemical Hydrogen Production describes the principles and materials challenges for the conversion of sunlight into hydrogen through water splitting at a semiconducting electrode. Readers will find an analysis of the solid state properties and materials requirements for semiconducting photo-electrodes, a detailed description of the semiconductor/electrolyte interface, in addition to the photo-electrochemical (PEC) cell. Experimental techniques to investigate both materials and PEC device performance are outlined, followed by an overview of the current state-of-the-art in PEC materials and devices, and combinatorial approaches towards the development of new materials. Finally, the economic and business perspectives of PEC devices are discussed, and promising future directions indicated. Photoelectrochemical Hydrogen Production is a one-stop resource for scientists, students and R&D practitioners starting in this field, providing both the theoretical background as well as useful practical information on photoelectrochemical measurement techniques. Experts in the field benefit from the chapters on current state-of-the-art materials/devices and future directions.
