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Haddad L, Gianolio D, Dunstan DJ, Liu Y, Rankine C, Sapelkin A. Quantifying intuition: Bayesian approach to figures of merit in EXAFS analysis of magic size clusters. NANOSCALE 2024. [PMID: 38414278 DOI: 10.1039/d3nr05110b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Analysis of the extended X-ray absorption fine structure (EXAFS) can yield local structural information in magic size clusters even when other structural methods (such as X-ray diffraction) fail, but typically requires an initial guess - an atomistic model. Model comparison is thus one of the most crucial steps in establishing atomic structure of nanoscale systems and relies critically on the corresponding figures of merit (delivered by the data analysis) to make a decision on the most suitable model of atomic arrangements. However, none of the currently used statistical figures of merit take into account the significant factor of parameter correlations. Here we show that ignoring such correlations may result in a selection of an incorrect structural model. We then report on a new metric based on Bayes theorem that addresses this problem. We show that our new metric is superior to the currently used in EXAFS analysis as it reliably yields correct structural models even in cases when other statistical criteria may fail. We then demonstrate the utility of the new figure of merit in comparison of structural models for CdS magic-size clusters using EXAFS data.
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Affiliation(s)
- Lucy Haddad
- QMUL, Mile End Road, London E1 4NS, UK.
- Diamond Light Source, Diamond House Harwell Science & Innovation Campus, Didcot OX11 0DE, UK
| | - Diego Gianolio
- Diamond Light Source, Diamond House Harwell Science & Innovation Campus, Didcot OX11 0DE, UK
| | | | - Ying Liu
- QMUL, Mile End Road, London E1 4NS, UK.
| | - Conor Rankine
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
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Chen Z, Ashokan A, Russo SP, Mulvaney P. Temperature Dependence of the CdS Bandgap in the Extreme Confinement Regime. NANO LETTERS 2023; 23:9287-9294. [PMID: 37811888 DOI: 10.1021/acs.nanolett.3c02368] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
A non-empirical equation describing the effect of size on the temperature dependence of the optical bandgap of CdS (dEg/dT) is obtained on the basis of the Brus equation. Intriguingly, we find that dEg/dT diverges strongly from bulk values only within the "extreme confinement" (EC) regime. We conducted both experimental and theoretical investigations of the absorption spectra of CdS clusters and quantum dots as a function of temperature above room temperature. Our results show that the value of dEg/dT obtained from absorption spectra in the EC regime is 2.5 times higher than in the strong confinement regime. Notable ligand sensitivities are also observed for dEg/dT in the case of CdS clusters. Ab initio molecular dynamics simulations and density functional theory calculations reveal that thermal fluctuations are the crucial factor influencing the bandgap temperature coefficient. Our results help resolve some long-standing debates regarding the dEg/dT behavior of semiconductor quantum dots.
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Affiliation(s)
- Zifei Chen
- ARC Centre of Excellence in Exciton Science, School of Chemistry, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Arun Ashokan
- ARC Centre of Excellence in Exciton Science, School of Chemistry, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Salvy P Russo
- ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Melbourne 3000, Australia
| | - Paul Mulvaney
- ARC Centre of Excellence in Exciton Science, School of Chemistry, The University of Melbourne, Melbourne, VIC 3010, Australia
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Chen Z, Manian A, Dong Y, Russo SP, Mulvaney P. Ligand and solvent effects on the absorption spectra of CdS magic-sized clusters. J Chem Phys 2023; 158:2887770. [PMID: 37129143 DOI: 10.1063/5.0147609] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 04/17/2023] [Indexed: 05/03/2023] Open
Abstract
The absorption spectra of congenetic wurtzite (WZ) and zincblende (ZB) CdS magic-sized clusters are investigated. We demonstrate that the exciton peak positions can be tuned by up to 500 meV by varying the strong coupling between X-type ligands and the semiconductor cores, while the addition of L-type ligands primarily affects cluster midgap states. When Z-type ligands are displaced by L-type ligands, red shifts in the absorption spectra are observed, despite the fact there is a small decrease in cluster size. Density functional theory calculations are used to explain these findings and they reveal the importance of Cd and S dangling bonds on the midgap states during the Z- to L-type ligand exchange process. Overall, ZB CdS clusters show higher chemical stability than WZ clusters but their optical properties exhibit greater sensitivity to the solvent. Conversely, WZ CdS clusters are not stable in a Lewis base-rich environment, resulting in various changes in their spectra. Our findings enable researchers to select capping ligands that modulate the optical properties of semiconductor clusters while maintaining precise control over their solvent interactions.
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Affiliation(s)
- Zifei Chen
- ARC Centre of Excellence in Exciton Science, School of Chemistry, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Anjay Manian
- ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Melbourne 3000, Australia
| | - Yihan Dong
- ARC Centre of Excellence in Exciton Science, School of Chemistry, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Salvy P Russo
- ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Melbourne 3000, Australia
| | - Paul Mulvaney
- ARC Centre of Excellence in Exciton Science, School of Chemistry, The University of Melbourne, Parkville, VIC 3010, Australia
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Sanmartín-Matalobos J, Bermejo-Barrera P, Aboal-Somoza M, Fondo M, García-Deibe AM, Corredoira-Vázquez J, Alves-Iglesias Y. Semiconductor Quantum Dots as Target Analytes: Properties, Surface Chemistry and Detection. NANOMATERIALS 2022; 12:nano12142501. [PMID: 35889725 PMCID: PMC9318497 DOI: 10.3390/nano12142501] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 07/17/2022] [Accepted: 07/19/2022] [Indexed: 02/04/2023]
Abstract
Since the discovery of Quantum Dots (QDs) by Alexey I. Ekimov in 1981, the interest of researchers in that particular type of nanomaterials (NMs) with unique optical and electrical properties has been increasing year by year. Thus, since 2009, the number of scientific articles published on this topic has not been less than a thousand a year. The increasing use of QDs due to their biomedical, pharmaceutical, biological, photovoltaics or computing applications, as well as many other high-tech uses such as for displays and solid-state lighting (SSL), has given rise to a considerable number of studies about its potential toxicity. However, there are a really low number of reported studies on the detection and quantification of QDs, and these include ICP–MS and electrochemical analysis, which are the most common quantification techniques employed for this purpose. The knowledge of chemical phenomena occurring on the surface of QDs is crucial for understanding the interactions of QDs with species dissolved in the dispersion medium, while it paves the way for a widespread use of chemosensors to facilitate its detection. Keeping in mind both human health and environmental risks of QDs as well as the scarcity of analytical techniques and methodological approaches for their detection, the adaptation of existing techniques and methods used with other NMs appears necessary. In order to provide a multidisciplinary perspective on QD detection, this review focused on three interrelated key aspects of QDs: properties, surface chemistry and detection.
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Affiliation(s)
- Jesús Sanmartín-Matalobos
- Coordination and Supramolecular Chemistry Group (SupraMetal), Department of Inorganic Chemistry, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (M.F.); (J.C.-V.); (Y.A.-I.)
- Correspondence: (J.S.-M.); (A.M.G.-D.)
| | - Pilar Bermejo-Barrera
- Trace Element, Speciation and Spectroscopy Group (GETEE), Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (P.B.-B.); (M.A.-S.)
| | - Manuel Aboal-Somoza
- Trace Element, Speciation and Spectroscopy Group (GETEE), Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (P.B.-B.); (M.A.-S.)
| | - Matilde Fondo
- Coordination and Supramolecular Chemistry Group (SupraMetal), Department of Inorganic Chemistry, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (M.F.); (J.C.-V.); (Y.A.-I.)
| | - Ana M. García-Deibe
- Coordination and Supramolecular Chemistry Group (SupraMetal), Department of Inorganic Chemistry, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (M.F.); (J.C.-V.); (Y.A.-I.)
- Correspondence: (J.S.-M.); (A.M.G.-D.)
| | - Julio Corredoira-Vázquez
- Coordination and Supramolecular Chemistry Group (SupraMetal), Department of Inorganic Chemistry, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (M.F.); (J.C.-V.); (Y.A.-I.)
| | - Yeneva Alves-Iglesias
- Coordination and Supramolecular Chemistry Group (SupraMetal), Department of Inorganic Chemistry, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (M.F.); (J.C.-V.); (Y.A.-I.)
- Trace Element, Speciation and Spectroscopy Group (GETEE), Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (P.B.-B.); (M.A.-S.)
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