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Diffusion of gold nanoparticles in porous silica monoliths determined by dynamic light scattering. J Colloid Interface Sci 2023; 641:251-264. [PMID: 36933471 DOI: 10.1016/j.jcis.2023.03.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 02/21/2023] [Accepted: 03/07/2023] [Indexed: 03/13/2023]
Abstract
HYPOTHESIS The applicability of the dynamic light scattering method for the determination of particle diffusivity under confinement without applying refractive index matching was not adequately explored so far. The confinement effect on particle diffusion in a porous material which is relevant for particle chromatography has also not yet been fully characterized. EXPERIMENTS Dynamic light scattering experiments were performed for unimodal dispersions of 11-mercaptoundecanoic acid-capped gold nanoparticles. Diffusion coefficients of gold nanoparticles in porous silica monoliths were determined without limiting refractive index matching fluids. Comparative experiments were also performed with the same nanoparticles and porous silica monolith but applying refractive index matching. FINDINGS Two distinct diffusivities could be determined inside the porous silica monolith, both smaller than that in free media, showing a slowing-down of the diffusion processes of nanoparticles under confinement. While the larger diffusivity can be related to the slightly slowed-down diffusion of particles in the bulk of the pores and in the necks connecting individual pores, the smaller diffusivity might be related to the diffusion of particles near the pore walls. It shows that the dynamic light scattering method with a heterodyne detection scheme can be used as a reliable and competitive tool for determining particle diffusion under confinement.
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Assessing the impact of increase in the number of hydroxyl groups on the microscopic behaviors of ammonium-based room temperature ionic liquids: A combined fluorescence up-conversion, fluorescence correlation and NMR spectroscopic study. J Photochem Photobiol A Chem 2023. [DOI: 10.1016/j.jphotochem.2022.114505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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3
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Kousik SR, Sipp D, Abitaev K, Li Y, Sottmann T, Koynov K, Atanasova P. From Macro to Mesoporous ZnO Inverse Opals: Synthesis, Characterization and Tracer Diffusion Properties. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:196. [PMID: 33466679 PMCID: PMC7828802 DOI: 10.3390/nano11010196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/08/2021] [Accepted: 01/10/2021] [Indexed: 11/16/2022]
Abstract
Oxide inverse opals (IOs) with their high surface area and open porosity are promising candidates for catalyst support applications. Supports with confined mesoporous domains are of added value to heterogeneous catalysis. However, the fabrication of IOs with mesoporous or sub-macroporous voids (<100 nm) continues to be a challenge, and the diffusion of tracers in quasi-mesoporous IOs is yet to be adequately studied. In order to address these two problems, we synthesized ZnO IOs films with tunable pore sizes using chemical bath deposition and template-based approach. By decreasing the size of polystyrene (PS) template particles towards the mesoporous range, ZnO IOs with 50 nm-sized pores and open porosity were synthesized. The effect of the template-removal method on the pore geometry (spherical vs. gyroidal) was studied. The infiltration depth in the template was determined, and the factors influencing infiltration were assessed. The crystallinity and photonic stop-band of the IOs were studied using X-Ray diffraction and UV-Vis, respectively. The infiltration of tracer molecules (Alexa Fluor 488) in multilayered quasi-mesoporous ZnO IOs was confirmed via confocal laser scanning microscopy, while fluorescence correlation spectroscopy analysis revealed two distinct diffusion times in IOs assigned to diffusion through the pores (fast) and adsorption on the pore walls (slow).
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Affiliation(s)
- Shravan R. Kousik
- Institute for Materials Science, University of Stuttgart, 70569 Stuttgart, Germany; (S.R.K.); (D.S.); (Y.L.)
| | - Diane Sipp
- Institute for Materials Science, University of Stuttgart, 70569 Stuttgart, Germany; (S.R.K.); (D.S.); (Y.L.)
| | - Karina Abitaev
- Institute of Physical Chemistry, University of Stuttgart, 70569 Stuttgart, Germany; (K.A.); (T.S.)
| | - Yawen Li
- Institute for Materials Science, University of Stuttgart, 70569 Stuttgart, Germany; (S.R.K.); (D.S.); (Y.L.)
| | - Thomas Sottmann
- Institute of Physical Chemistry, University of Stuttgart, 70569 Stuttgart, Germany; (K.A.); (T.S.)
| | - Kaloian Koynov
- Max Planck Institute for Polymer Research, 55128 Mainz, Germany
| | - Petia Atanasova
- Institute for Materials Science, University of Stuttgart, 70569 Stuttgart, Germany; (S.R.K.); (D.S.); (Y.L.)
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Angiolini JF, Stortz M, Steinberg PY, Mocskos E, Bruno L, Soler-Illia G, Angelomé PC, Wolosiuk A, Levi V. Diffusion of single dye molecules in hydrated TiO2 mesoporous films. Phys Chem Chem Phys 2017; 19:26540-26544. [DOI: 10.1039/c7cp05186g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Fluorescence correlation spectroscopy (FCS) shows how the pore dimensions of thin and hydrated TiO2 mesoporous calcined films modulate the diffusion of molecules across the pore network.
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Affiliation(s)
- Juan F. Angiolini
- Universidad de Buenos Aires
- Facultad de Ciencias Exactas y Naturales
- Departamento de Química Biológica
- Argentina-CONICET – Universidad de Buenos Aires
- Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN)
| | - Martín Stortz
- CONICET – Universidad de Buenos Aires
- Instituto de Fisiología
- Biología Molecular y Neurociencias (IFIBYNE)
- Buenos Aires
- Argentina
| | - Paula Y. Steinberg
- Gerencia Química – Centro Atómico Constituyentes – Comisión Nacional de Energía Atómica
- CONICET
- San Martín
- Argentina
| | - Esteban Mocskos
- Universidad de Buenos Aires
- Facultad de Ciencias Exactas y Naturales
- Departamento de Computación
- Buenos Aires, Argentina-CONICET
- Centro de Simulación Computacional para Aplicaciones Tecnológicas (CSC)
| | - Luciana Bruno
- CONICET – Universidad de Buenos Aires
- Instituto de Física de Buenos Aires (IFIBA)
- Buenos Aires
- Argentina
| | - Galo Soler-Illia
- Instituto de Nanosistemas
- UNSAM, 25 de Mayo y Francia (1650)
- San Martín
- Argentina
| | - Paula C. Angelomé
- Gerencia Química – Centro Atómico Constituyentes – Comisión Nacional de Energía Atómica
- CONICET
- San Martín
- Argentina
| | - Alejandro Wolosiuk
- Gerencia Química – Centro Atómico Constituyentes – Comisión Nacional de Energía Atómica
- CONICET
- San Martín
- Argentina
- Departamento de Química Inorgánica
| | - Valeria Levi
- Universidad de Buenos Aires
- Facultad de Ciencias Exactas y Naturales
- Departamento de Química Biológica
- Argentina-CONICET – Universidad de Buenos Aires
- Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN)
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5
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Over B, Rathke B, Will S. Investigations on particle diffusion in porous glass by angle-dependent dynamic light scattering. J Mol Liq 2016. [DOI: 10.1016/j.molliq.2016.07.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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6
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Xie J, Doroshenko M, Jonas U, Butt HJ, Koynov K. Temperature-Controlled Diffusion in PNIPAM-Modified Silica Inverse Opals. ACS Macro Lett 2016; 5:190-194. [PMID: 35614698 DOI: 10.1021/acsmacrolett.5b00895] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report a new strategy for the preparation of well-defined and mechanically stable porous nanostructures with tunable porosity. Silica inverse opals, which are known as a model system for a porous periodic nanostructure, were grafted with brushes of the thermoresponsive poly(N-isopropylacrylamide) grown via atom transfer radical polymerization. By tuning the temperature, the swelling state of the brush layer is reversibly altered, and with this we were able to control the overall porosity of the system and, thus, the mobility of small penetrants. Fluorescence correlation spectroscopy, a method combining single molecule sensitivity with small probing volume (<1 μm3), was used to directly monitor and quantify in situ the changes in the penetrants' mobility.
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Affiliation(s)
- Jing Xie
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Mikheil Doroshenko
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Ulrich Jonas
- Macromolecular Chemistry, Department Chemistry−Biology, University of Siegen, Adolf-Reichwein-Strasse 2, AR-G 213, D-57076 Siegen, Germany
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Kaloian Koynov
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
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7
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Schneider D, Mehlhorn D, Zeigermann P, Kärger J, Valiullin R. Transport properties of hierarchical micro–mesoporous materials. Chem Soc Rev 2016; 45:3439-67. [DOI: 10.1039/c5cs00715a] [Citation(s) in RCA: 167] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This work provides an overview of different experimental techniques of diffusion measurements in porous materials and discusses transport properties of several classes of hierarchically organized micro-mesoporous materials.
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Affiliation(s)
- Daniel Schneider
- Faculty of Physics and Earth Sciences
- University of Leipzig
- Leipzig
- Germany
| | - Dirk Mehlhorn
- Faculty of Physics and Earth Sciences
- University of Leipzig
- Leipzig
- Germany
| | - Philipp Zeigermann
- Faculty of Physics and Earth Sciences
- University of Leipzig
- Leipzig
- Germany
| | - Jörg Kärger
- Faculty of Physics and Earth Sciences
- University of Leipzig
- Leipzig
- Germany
| | - Rustem Valiullin
- Faculty of Physics and Earth Sciences
- University of Leipzig
- Leipzig
- Germany
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Higgins DA, Park SC, Tran-Ba KH, Ito T. Single-Molecule Investigations of Morphology and Mass Transport Dynamics in Nanostructured Materials. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2015; 8:193-216. [PMID: 26132347 DOI: 10.1146/annurev-anchem-071114-040153] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Nanostructured materials such as mesoporous metal oxides and phase-separated block copolymers form the basis for new monolith, membrane, and thin film technologies having applications in energy storage, chemical catalysis, and separations. Mass transport plays an integral role in governing the application-specific performance characteristics of many such materials. The majority of methods employed in their characterization provide only ensemble data, often masking the nanoscale, molecular-level details of materials morphology and mass transport. Single-molecule fluorescence methods offer direct routes to probing these characteristics on a single-molecule/single-nanostructure basis. This article provides a review of single-molecule studies focused on measurements of anisotropic diffusion, adsorption, partitioning, and confinement in nanostructured materials. Experimental methods covered include confocal and wide-field fluorescence microscopy. The results obtained promise to deepen our understanding of mass transport mechanisms in nanostructures, thus aiding in the realization of advanced materials systems.
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Affiliation(s)
- Daniel A Higgins
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506-0401; ,
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Basak S, Chattopadhyay K. Fluorescence correlation spectroscopy study on the effects of the shape and size of a protein on its diffusion inside a crowded environment. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:14709-14717. [PMID: 24180214 DOI: 10.1021/la4031987] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Fluorescence correlation spectroscopy (FCS) has been commonly used to study the diffusional and conformational fluctuations of labeled molecules at single-molecule resolution. Here, we explored the applications of FCS inside a polyacrylamide gel to study the effects of molecular weight and molecular shape in a crowded environment. To understand the effect of molecular weight, we carried out FCS experiments with four model systems of different molecular weights in the presence of varying concentrations of acrylamide. The correlation curves were fit adequately using a model containing two diffusing components: one representing unhindered diffusion and one representing slow hindered diffusion in the gel phase. A large number of measurements carried out at different randomly chosen spots on a gel were used to determine the most probable diffusion time values using Gaussian distribution analysis. The variation of the diffusivity with the molecular weight of the model systems could be represented well using the effective medium model. This model assumes a combination of hydrodynamic and steric effects on solute diffusivity. To study the effects of solute shape, FCS experiments were carried inside a urea gradient gel to probe the urea-induced unfolding transition of Alexa488Maleimide-labeled bovine serum albumin. We showed that the scaling behavior, relating the hydrodynamic radius and the number of amino acids, changes inside an acrylamide gel for both folded and unfolded proteins. We showed further that crowding induced by a polyacrylamide gel increases the resolution of measuring the difference in hydrodynamic radii between the unfolded and folded states.
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Affiliation(s)
- Sujit Basak
- Protein Folding and Dynamics Laboratory, Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology , 4 Raja S. C. Mullick Road, Kolkata 700032, India
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Fowlkes JD, Collier CP. Single-molecule mobility in confined and crowded femtolitre chambers. LAB ON A CHIP 2013; 13:877-885. [PMID: 23303284 DOI: 10.1039/c2lc40907k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The effects of increased crowding and confinement on the mobility of individual fluorescent molecules were studied using Fluorescence Correlation Spectroscopy (FCS) in a microfluidic device with sealable femtolitre-volume chambers, and compared to three dimensional stochastic Monte Carlo simulations. When crowding and the degree of confinement were increased simultaneously, extended correlation times of fluorescent intensity fluctuations were observed with FCS compared to varying either crowding or confinement alone. Both experimental data and simulation suggest these extended correlation times were due to increased fluorophore adsorption-desorption events at the chamber lid in the presence of crowders. The data in increasingly confined and crowded chambers described here captures some of the salient features of crowding in cell-like environments.
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Affiliation(s)
- Jason D Fowlkes
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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11
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Koynov K, Butt HJ. Fluorescence correlation spectroscopy in colloid and interface science. Curr Opin Colloid Interface Sci 2012. [DOI: 10.1016/j.cocis.2012.09.003] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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12
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Patra S, Samanta A. Microheterogeneity of Some Imidazolium Ionic Liquids As Revealed by Fluorescence Correlation Spectroscopy and Lifetime Studies. J Phys Chem B 2012; 116:12275-83. [DOI: 10.1021/jp3061202] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Satyajit Patra
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India
| | - Anunay Samanta
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India
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Chowdhury SA, Lim MH. Specific Binding of Nile Red to Apomyoglobin. JOURNAL OF THE KOREAN CHEMICAL SOCIETY-DAEHAN HWAHAK HOE JEE 2011. [DOI: 10.5012/jkcs.2011.55.5.746] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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14
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Kirkeminde AW, Torres T, Ito T, Higgins DA. Multiple Diffusion Pathways in Pluronic F127 Mesophases Revealed by Single Molecule Tracking and Fluorescence Correlation Spectroscopy. J Phys Chem B 2011; 115:12736-43. [DOI: 10.1021/jp208234b] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alec W. Kirkeminde
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506-0401, United States
| | - Travis Torres
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506-0401, United States
| | - Takashi Ito
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506-0401, United States
| | - Daniel A. Higgins
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506-0401, United States
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Sanguigno L, De Santo I, Causa F, Netti PA. Fluorescence Correlation Spectroscopy in Semiadhesive Wall Proximity. Anal Chem 2011; 83:8101-7. [DOI: 10.1021/ac201116g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Luigi Sanguigno
- Center for Advanced Biomaterials for Health Care@CRIB, Istituto Italiano di Tecnologia, P.le Tecchio 80, 80125 Naples, Italy
| | - Ilaria De Santo
- Center for Advanced Biomaterials for Health Care@CRIB, Istituto Italiano di Tecnologia, P.le Tecchio 80, 80125 Naples, Italy
| | - Filippo Causa
- Interdisciplinary Research Centre on Biomaterials, University of Naples Federico II, P.le Tecchio 80, 80125 Naples, Italy
| | - Paolo A. Netti
- Center for Advanced Biomaterials for Health Care@CRIB, Istituto Italiano di Tecnologia, P.le Tecchio 80, 80125 Naples, Italy
- Interdisciplinary Research Centre on Biomaterials, University of Naples Federico II, P.le Tecchio 80, 80125 Naples, Italy
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16
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Chowdhury SA, Lim MH. Characterization of the Surface Contribution to Fluorescence Correlation Spectroscopy Measurements. B KOREAN CHEM SOC 2011. [DOI: 10.5012/bkcs.2011.32.2.583] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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17
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Guo J, Baker GA, Hillesheim PC, Dai S, Shaw RW, Mahurin SM. Fluorescence correlation spectroscopy evidence for structural heterogeneity in ionic liquids. Phys Chem Chem Phys 2011; 13:12395-8. [DOI: 10.1039/c1cp20929a] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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18
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Haramagatti CR, Schacher FH, Müller AHE, Köhler J. Diblock copolymer membranes investigated by single-particle tracking. Phys Chem Chem Phys 2011; 13:2278-84. [DOI: 10.1039/c0cp01658f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Cherdhirankorn T, Retsch M, Jonas U, Butt HJ, Koynov K. Tracer diffusion in silica inverse opals. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:10141-10146. [PMID: 20232884 DOI: 10.1021/la1002572] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We employed fluorescence correlation spectroscopy (FCS) to study the diffusion of small fluorescence tracers in liquid filled silica inverse opals. The inverse opals consisted of a nanoporous silica scaffold spanning a hexagonal crystal of spherical voids of 360 nm diameter connected by circular pores of 70 nm diameter. The diffusion of Alexa Fluor 488 in water and of perylene-3,4,9,10-tetracarboxylic diimide (PDI) in toluene was studied. Three diffusion modes could be distinguished: (1) Free diffusion limited by the geometric constraints given by the inverse opal, where, as compared to the free solution, this diffusion is slowed down by a factor of 3-4, (2) slow diffusion inside the nanoporous matrix of the silica scaffold, and (3) diffusion limited by adsorption. On the length scale of the focus of a confocal microscope of roughly 400 nm diffusion was non-Fickian in all cases.
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De Santo I, Causa F, Netti PA. Subdiffusive Molecular Motion in Nanochannels Observed by Fluorescence Correlation Spectroscopy. Anal Chem 2010; 82:997-1005. [DOI: 10.1021/ac902270k] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ilaria De Santo
- Interdisciplinary Research Centre on Biomaterials (CRIB), University Federico II, Piazzale Tecchio 80, 80125, Naples, Italy, Italian Institute of Technology (IIT), Via Morego, 30 Genoa, Italy, and Department of Experimental and Clinical Medicine, University Magna Graecia, Germaneto, 88100, Catanzaro, Italy
| | - Filippo Causa
- Interdisciplinary Research Centre on Biomaterials (CRIB), University Federico II, Piazzale Tecchio 80, 80125, Naples, Italy, Italian Institute of Technology (IIT), Via Morego, 30 Genoa, Italy, and Department of Experimental and Clinical Medicine, University Magna Graecia, Germaneto, 88100, Catanzaro, Italy
| | - Paolo A. Netti
- Interdisciplinary Research Centre on Biomaterials (CRIB), University Federico II, Piazzale Tecchio 80, 80125, Naples, Italy, Italian Institute of Technology (IIT), Via Morego, 30 Genoa, Italy, and Department of Experimental and Clinical Medicine, University Magna Graecia, Germaneto, 88100, Catanzaro, Italy
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De Cremer G, Sels BF, De Vos DE, Hofkens J, Roeffaers MBJ. Fluorescence micro(spectro)scopy as a tool to study catalytic materials in action. Chem Soc Rev 2010; 39:4703-17. [DOI: 10.1039/c0cs00047g] [Citation(s) in RCA: 144] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Zhou Y, Yip WT. Balance between Coulombic interactions and physical confinement in silica hydrogel encapsulation. J Phys Chem B 2009; 113:5720-7. [PMID: 19344099 DOI: 10.1021/jp8036473] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We examined the behavior of various entrapped guest molecules within silica hydrogel and evaluated the effect of Coulombic interactions and physical confinement on molecular mobility. Although rhodamine 6G (R6G) and fluorescein (FL) share similar size and molecular structure, their behavior in silica hydrogel was found to be dramatically different. A good majority of R6G was immobilized with little to no exchangeable molecules, whereas FL displayed a considerable amount of mobility in silica hydrogel. Moreover, silica hydrogel encapsulated R6G failed to gain mobility even under low pH or high ionic strength conditions to minimize Coulombic interactions, implying that encapsulated R6G molecules were inaccessible and likely trapped deep inside the silica matrix of a hydrogel. On the contrary, FL was relatively free to rotate and translate inside a silica hydrogel, implying that FL remained solvated in the solvent phase and was able to maintain its mobility throughout the hydrogel formation process. Fluorescence recovery after photobleaching measurements put the diffusion coefficient of FL in silica hydrogel at ca. 2.1 x 10(-6) cm(2) s(-1), about a factor of 3 slower than that in solution. The substantial difference in mobility between cationic R6G and anionic FL led us to conclude that the effect of Coulombic interactions on mobility is more dominating in hydrogel than in alcogel. Our results also suggest that Coulombic interactions are strong enough to influence the eventual placement of a guest molecule in a silica hydrogel, causing R6G and FL to reside in different microenvironments. This has a profound implication on the use of molecular probes to study silica hydrogel since a slight difference in physical attribute may result in very diverse observations even from identically prepared silica hydrogel samples. As demonstrated, the repulsion between FL and silica renders FL liquid-bound, making FL more suitable for monitoring the change in viscosity and physical confinement during hydrogel formation, whereas other researchers have shown that silica-bound R6G is more suitably used as a reliable probe for monitoring the growth of silica colloids because of its strong attraction toward silica.
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Affiliation(s)
- Yongyao Zhou
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, USA
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Ye F, Collinson MM, Higgins DA. What can be learned from single molecule spectroscopy? Applications to sol-gel-derived silica materials. Phys Chem Chem Phys 2008; 11:66-82. [PMID: 19081909 DOI: 10.1039/b812924j] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Single molecule spectroscopic methods are now being widely employed to probe the nanometer scale properties of sol-gel-derived silica materials. This article reviews a subset of the recent literature in this area and provides salient examples of the new information that can be obtained. The materials covered include inorganic and organically-modified silica, along with surfactant-templated mesoporous materials. Studies of molecule-matrix interactions based on ionic, hydrogen bonding and hydrophobic interactions are reviewed, highlighting the impacts of these interactions on mass transport phenomena. Quantitative investigations of molecular diffusion by single molecule tracking and fluorescence correlation spectroscopy are also covered, focusing on the characterization of anisotropic and hindered diffusion in mesoporous systems. Single molecule polarity studies are described and the new information that can be obtained from the resulting inhomogeneous distributions is discussed. Likewise, single molecule studies of silica acidity properties are reviewed, including observation of nanoscale buffering phenomena due to the chemistry of surface silanols. Finally, related single nanoparticle studies of macroporous silicas are also discussed.
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Affiliation(s)
- Fangmao Ye
- Department of Chemistry, Kansas State University, KS, 66506, Manhattan, USA
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Sekiguchi K, Yamaguchi S, Tahara T. Femtosecond time-resolved electronic sum-frequency generation spectroscopy: A new method to investigate ultrafast dynamics at liquid interfaces. J Chem Phys 2008; 128:114715. [DOI: 10.1063/1.2841023] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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Affiliation(s)
- Tetsuo Okada
- Department of Chemistry, Tokyo Institute of Technology
| | - Yuiko Tasaki
- Department of Chemistry, Tokyo Institute of Technology
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Ye F, Collinson MM, Higgins DA. Molecular orientation and its influence on autocorrelation amplitudes in single-molecule imaging experiments. Anal Chem 2007; 79:6465-72. [PMID: 17663532 DOI: 10.1021/ac071255z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The concentration dependence of autocorrelation amplitudes obtained from orientationally fixed single molecules is explored using theory, simulation, and experimental results. Autocorrelation amplitudes obtained under such circumstances are shown to be approximately 2-fold larger than predicted in previous studies (Koppel, D. E. Phys. Rev. A 1974, 10, 1938-1945 and citing references), which frequently assume polarization-independent excitation and detection. A detailed derivation of the autocorrelation amplitude expected under conditions frequently employed in single-molecule experiments is given. Simulated and experimental single-molecule image data obtained from samples incorporating fixed single molecules are used to verify the correctness of the model. These results are compared to both simulated and experimental time transient data in which the molecules exhibit predominantly fast rotational reorientation and to which previously reported models apply. The experimental results employed are obtained from dye-doped mesoporous silica thin films studied at different levels of hydration. The theory and results obtained are of importance to the determination of molecular concentrations from single-molecule image and time transient autocorrelation data, in situations where the molecules exhibit permanent or reversible adsorption at fixed orientations in or on thin-film materials.
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Affiliation(s)
- Fangmao Ye
- Department of Chemistry, Kansas State University, Manhattan, KS 66506, USA
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27
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Jung C, Hellriegel C, Platschek B, Wöhrle D, Bein T, Michaelis J, Bräuchle C. Simultaneous Measurement of Orientational and Spectral Dynamics of Single Molecules in Nanostructured Host−Guest Materials. J Am Chem Soc 2007; 129:5570-9. [PMID: 17408267 DOI: 10.1021/ja0684850] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nanostructured host-guest materials are important for various applications in nanoscience, and therefore, a thorough understanding of the dynamics of the guest molecules within the host matrix is needed. To this aim we used single-molecule fluorescence techniques to simultaneously examine the spectral and the orientational behavior of single molecules in nanostructured porous host materials. Two types of host-guest systems have been investigated. First, oxazine-1 dye molecules were fixed rigidly in the channels of microporous AlPO4-5 crystals. Second, it was shown that terrylenediimide (TDI) dye molecules move in the mesoporous network of an uncalcined M41S thin film. In the first sample both spectral fluctuations ( approximately 5 nm) and rare spectral jumps (>10 nm) of the emission maximum were observed. However, the orientation of the emission dipole of the dye molecules remained constant. In contrast, the second system showed orientational dynamics as well as substantially more spectral dynamics. In this system the molecules were found to move between different regions in the host. The typical motion of the TDI molecules in the pores of M41S was not continuous but characterized by jumps between specific sites. Moreover, the spectral and orientational dynamics were correlated and arose directly from the different environments that were being explored by the mobile molecule.
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Affiliation(s)
- Christophe Jung
- Department of Chemistry und Biochemistry, Nanosystems Initiative Munich, Ludwig-Maximilians-Universität München, Butenandtstrasse 11, D-81377 München, Germany
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28
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Hohlbein J, Steinhart M, Schiene-Fischer C, Benda A, Hof M, Hübner CG. Confined diffusion in ordered nanoporous alumina membranes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2007; 3:380-5. [PMID: 17285657 DOI: 10.1002/smll.200600398] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Affiliation(s)
- J Hohlbein
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
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29
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Sanabria H, Kubota Y, Waxham MN. Multiple diffusion mechanisms due to nanostructuring in crowded environments. Biophys J 2006; 92:313-22. [PMID: 17040979 PMCID: PMC1697840 DOI: 10.1529/biophysj.106.090498] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
One of the key questions regarding intracellular diffusion is how the environment affects molecular mobility. Mostly, intracellular diffusion has been described as hindered, and the physical reasons for this behavior are: immobile barriers, molecular crowding, and binding interactions with immobile or mobile molecules. Using results from multi-photon fluorescence correlation spectroscopy, we describe how immobile barriers and crowding agents affect translational mobility. To study the hindrance produced by immobile barriers, we used sol-gels (silica nanostructures) that consist of a continuous solid phase and aqueous phase in which fluorescently tagged molecules diffuse. In the case of molecular crowding, translational mobility was assessed in increasing concentrations of 500 kDa dextran solutions. Diffusion of fluorescent tracers in both sol-gels and dextran solutions shows clear evidence of anomalous subdiffusion. In addition, data from the autocorrelation function were analyzed using the maximum entropy method as adapted to fluorescence correlation spectroscopy data and compared with the standard model that incorporates anomalous diffusion. The maximum entropy method revealed evidence of different diffusion mechanisms that had not been revealed using the anomalous diffusion model. These mechanisms likely correspond to nanostructuring in crowded environments and to the relative dimensions of the crowding agent with respect to the tracer molecule. Analysis with the maximum entropy method also revealed information about the degree of heterogeneity in the environment as reported by the behavior of diffusive molecules.
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Affiliation(s)
- Hugo Sanabria
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.
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30
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Fu Y, Ye F, Sanders WG, Collinson MM, Higgins DA. Single Molecule Spectroscopy Studies of Diffusion in Mesoporous Silica Thin Films. J Phys Chem B 2006; 110:9164-70. [PMID: 16671729 DOI: 10.1021/jp054178p] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Single molecule spectroscopy is applied in studies of diffusion and surface adsorption in sol-gel-derived mesoporous silica thin films. Mesoporous films are obtained by spin casting surfactant-templated sols onto glass substrates. Small-angle X-ray diffraction results are consistent with hexagonally ordered mesophases in as-synthesized (i.e., surfactant-containing) films. Upon calcination, a 30% contraction and disordering of these structures occurs. Nile Red is used as a fluorescent probe of both the as-synthesized and calcined films. It is loaded into the samples at subnanomolar levels either prior to spin casting or after calcination. Fluorescence imaging and single-point fluorescence time transients show the dye molecules to be relatively mobile in the as-synthesized samples. In contrast, the molecules appear entrapped at fixed locations in dry calcined films. In calcined films rehydrated under high humidity conditions, the Nile Red molecules again become mobile. Time transients obtained from the as-synthesized and rehydrated samples provide clear evidence for frequent reversible adsorption of the dye to the silica surfaces. Autocorrelations of the time transients provide quantitative data on the mean diffusion coefficients (D = 2.4 x 10(-10) and 2.6 x 10(-10) cm2/s) and mean desorption times (1/k = 25 and 40 s) for the as-synthesized and rehydrated films, respectively. The results prove both water and surfactant play important roles in governing matrix interactions and mass transport.
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Affiliation(s)
- Yi Fu
- Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, USA
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31
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Higgins DA, Collinson MM. Gaining insight into the nanoscale properties of sol-gel-derived silicate thin films by single-molecule spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:9023-31. [PMID: 16171328 DOI: 10.1021/la050384c] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The application of single-molecule spectroscopic methods in studies of individual nanoscale environments within sol-gel-derived silicate thin films is reviewed. Representative examples of the experiments performed and results obtained in several studies from the authors' laboratories are given. Included are investigations of the static and dynamic polarity properties of organically modified silicate (ORMOSIL) films. The results of these studies point to nonrandom variations in the film properties, providing strong evidence for the formation of phase-separated organic- and inorganic-rich domains. Studies of single-molecule diffusion through the same films yield important evidence for the formation of liquidlike silicate oligomers that facilitate probe molecule diffusion. Finally, single-molecule studies of the local pH within individual film environments are discussed. Valuable information on the contributions of local materials' acidity variations to overall sample heterogeneity is obtained. The results of immersion studies indicate that certain molecular environments are inaccessible to external solutions over periods as long as a few hours. The article concludes with a discussion of possible future challenges in this research that may be addressed by new and existing single-molecule methods.
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Affiliation(s)
- Daniel A Higgins
- Department of Chemistry, Kansas State University, Manhattan, KS 66506, USA.
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32
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Egelhaaf HJ, Rademann J. Understanding Supported Reactions in Spherical Compartments: A General Algorithm To Model and Determine Rate Constants, Diffusion Coefficients, and Spatial Product Distributions. ACTA ACUST UNITED AC 2005; 7:929-41. [PMID: 16283804 DOI: 10.1021/cc050015z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A general algorithm allowing the numerical modeling of the time and space dependence of product formation in spherical reaction volumes is described. The algorithm is described by the complete set of mass balance equations. On the basis of these equations, the effects of the diffusion coefficient, reaction rate, bead size, reagent excess, and packing density of the resin beads on the overall reaction rates are determined for second-order reactions. Experimental data of reaction progress are employed to calculate reaction rates and diffusion coefficients in polymer-supported reactions. In addition, the conditions for shell-like product formation are determined, and various strategies for the radial patterning of resin beads are compared. The effect of diffusion on polymer-supported enzyme-catalyzed reactions of the Michaelis-Menten type is treated, as well. Finally, the effects of typical nonideal solid-phase phenomena, namely, the inhomogeneity of rate constants and the concentration dependence of diffusion coefficients, on overall rates are discussed.
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Affiliation(s)
- Hans-Joachim Egelhaaf
- Medicinal Chemistry, Leibniz Institute for Molecular Pharmacology (FMP), Berlin, Germany
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33
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Zhong Z, Lowry M, Wang G, Geng L. Probing Strong Adsorption of Solute onto C18-Silica Gel by Fluorescence Correlation Imaging and Single-Molecule Spectroscopy under RPLC Conditions. Anal Chem 2005; 77:2303-10. [PMID: 15828761 DOI: 10.1021/ac048290f] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding molecular adsorption at a chromatographic interface is of great interest for addressing the tailing problem in chemical separations. Single-molecule spectroscopy and confocal fluorescence correlation imaging are used to study the adsorption sites of C(18) silica beads under RPLC chromatographic conditions. The experiments show that cationic molecule rhodamine 6G laterally diffuses through the chromatographic interface of a C(18) hydrocarbon monolayer and acetonitrile with occasional reversible strong adsorptions. Fluorescence correlation imaging extracts the rare strong adsorption events from large data sets, revealing that the strong adsorption sites are randomly distributed throughout the silica beads. Virtually every imaging pixel of silica beads adsorbs molecules. Single-molecule spectroscopy of the 584 strong adsorption events observed indicates that the strong adsorptions persist on the time scales from several milliseconds to seconds, having an average desorption time of 61 ms. The strong adsorption events are rare, comprising 0.3% of the total observation time. The sizes of strong adsorption sites are within the optical resolution of confocal imaging.
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Affiliation(s)
- Zhenming Zhong
- Department of Chemistry, Optical Science and Technology Center, University of Iowa, Iowa City, Iowa 52242, USA
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34
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Kanungo M, Collinson MM. Controlling diffusion in sol-gel derived monoliths. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:827-829. [PMID: 15667155 DOI: 10.1021/la047518r] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Redox probes were trapped within a silica monolith prepared in part with organoalkoxysilanes containing a quaternary ammonium functional group. The diffusion coefficients of the entrapped molecules were measured as the gels were slowly dried using chronoamperometry and cyclic voltammetry with ultramicroelectrodes. Gel-entrapped cobalt(II) tris(bipyridine) (Co(bpy)(3)(2+)) diffuses at rates similar to that measured in the sols by incorporating a small amount of the positively charged functional group in the matrix. In comparison, the diffusion coefficient of gel-entrapped ferricyanide (Fe(CN)(6)(3-)) drops an order of magnitude relative to its value in the sol soon after gelation. These results demonstrate the ease at which diffusion in hydrated gels can be easily controlled by simply changing the charge on the walls of the silica host.
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Affiliation(s)
- Mandakini Kanungo
- Department of Chemistry, Kansas State University, Manhattan, KS 66506-3701, USA
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35
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Walcarius A, Mandler D, Cox JA, Collinson M, Lev O. Exciting new directions in the intersection of functionalized sol–gel materials with electrochemistry. ACTA ACUST UNITED AC 2005. [DOI: 10.1039/b504839g] [Citation(s) in RCA: 242] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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36
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Martin-Brown SA, Fu Y, Saroja G, Collinson MM, Higgins DA. Single-Molecule Studies of Diffusion by Oligomer-Bound Dyes in Organically Modified Sol−Gel-Derived Silicate Films. Anal Chem 2004; 77:486-94. [PMID: 15649044 DOI: 10.1021/ac0491511] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Single-molecule fluorescence spectroscopy is used to study dye diffusion within organically modified silicate (ORMOSIL) films. ORMOSIL films are prepared from sols containing tetraethoxysilane and isobutyltrimethoxysilane in 2:1 and 1:9 molar ratios. Nile red and a new silanized form of nile red that can be covalently attached to the silicate matrix are used as fluorescent probe molecules. The number and rate of single molecules diffusing through these films increases dramatically with increasing film organic content. Autocorrelation of the fluorescence images yields a quantitative measure of the relative populations of fixed and diffusing species. Surprisingly, both "free" and silicate-bound nile red exhibit relatively facile translational motions. Single-molecule/single-point fluorescence correlation spectroscopy (FCS) is used to measure the dye diffusion coefficients in submicrometer-scale film regions. The most common diffusion coefficients for "free" and silicate-bound nile red molecules in the 1:9 films are 3.9 x 10(-10) and 1.6 x 10(-10) cm(2)/s, respectively. The unexpectedly rapid diffusion of silicate-bound nile red is attributed to the presence of liquidlike silicate oligomers in the films. A lower bound for the molecular weight of the oligomers is estimated at 2900. Bulk solution-phase FCS experiments performed on "free" and silicate-bound nile red species extracted into chloroform solutions provide valuable support for these conclusions. Comparison of the results derived from experimental and simulated time transients indicates film heterogeneity occurs on sub-100-nm-length scales and likely results from the presence of inorganic- and organic-rich domains.
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Affiliation(s)
- Skylar A Martin-Brown
- Department of Chemistry, Kansas State University, 111 Willard Hall, Manhattan, Kansas 66506, USA
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37
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Hellriegel C, Kirstein J, Bräuchle C, Latour V, Pigot T, Olivier R, Lacombe S, Brown R, Guieu V, Payrastre C, Izquierdo A, Mocho P. Diffusion of Single Streptocyanine Molecules in the Nanoporous Network of Sol−Gel Glasses. J Phys Chem B 2004. [DOI: 10.1021/jp049412a] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christian Hellriegel
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Johanna Kirstein
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Christoph Bräuchle
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Virginie Latour
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Thierry Pigot
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Rémi Olivier
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Sylvie Lacombe
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Ross Brown
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Valérie Guieu
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Corinne Payrastre
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Albert Izquierdo
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
| | - Pierre Mocho
- Department Chemie and CeNS, Ludwig-Maximilians Universität München, Butenandtstr. 11, 81377 München, Germany, Laboratoire de Chimie Théorique et de Physico-Chimie Moléculaire, umr 5624 du CNRS et de l'Université de Pau et des pays de l'Adour, IFR, rue Jules Ferry, 64075 Pau Cedex, France, Laboratoire de Synthèse et de Physico-Chimie de Molécules d'Intérêt Biologique, umr 5068 du CNRS et de l'Université Paul Sabatier de Toulouse, 118 route de Narbonne, 31062 Toulouse Cedex 04, France, and Laboratoire de
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