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Miki H, Ishigami T, Yamanaka J, Okuzono T, Toyotama A, Mata J, Komazawa H, Takeda Y, Minami M, Fujita M, Doi M, Higuchi T, Takase H, Adachi S, Sakashita T, Shimaoka T, Nagai M, Watanabe Y, Fukuyama S. Clustering of charged colloidal particles in the microgravity environment of space. NPJ Microgravity 2023; 9:33. [PMID: 37120425 PMCID: PMC10148850 DOI: 10.1038/s41526-023-00280-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 04/12/2023] [Indexed: 05/01/2023] Open
Abstract
We conducted a charge-charge clustering experiment of positively and negatively charged colloidal particles in aqueous media under a microgravity environment at the International Space Station. A special setup was used to mix the colloid particles in microgravity and then these structures were immobilized in gel cured using ultraviolet (UV) light. The samples returned to the ground were observed by optical microscopy. The space sample of polystyrene particles with a specific gravity ρ (=1.05) close to the medium had an average association number of ~50% larger than the ground control and better structural symmetry. The effect of electrostatic interactions on the clustering was also confirmed for titania particles (ρ ~ 3), whose association structures were only possible in the microgravity environment without any sedimentation they generally suffer on the ground. This study suggests that even slight sedimentation and convection on the ground significantly affect the structure formation of colloids. Knowledge from this study will help us to develop a model which will be used to design photonic materials and better drugs.
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Affiliation(s)
- Hiroyuki Miki
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Teruyoshi Ishigami
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Junpei Yamanaka
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan.
| | - Tohru Okuzono
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Akiko Toyotama
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Jitendra Mata
- Australian Centre for Neutron Scattering (ACNS), Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW, 2234, Australia
| | - Honoka Komazawa
- Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Yushi Takeda
- Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Madoka Minami
- Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Minori Fujita
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Maho Doi
- Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Tsunehiko Higuchi
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Hiroshi Takase
- Core Laboratory, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho, Nagoya, Japan
| | - Satoshi Adachi
- Japan Aerospace Exploration Agency (JAXA), 2-1-1 Sengen, Tsukuba, Japan
| | - Tetsuya Sakashita
- Japan Aerospace Exploration Agency (JAXA), 2-1-1 Sengen, Tsukuba, Japan
| | - Taro Shimaoka
- Japan Space Forum (JSF), 3-2-1 Kandasurugadai, Chiyoda, Tokyo, Japan
| | - Masae Nagai
- Japan Space Forum (JSF), 3-2-1 Kandasurugadai, Chiyoda, Tokyo, Japan
| | - Yuki Watanabe
- Advanced Engineering Services (AES) Co., Ltd., 1-6-1 Takezono, Tsukuba, Japan
| | - Seijiro Fukuyama
- Advanced Engineering Services (AES) Co., Ltd., 1-6-1 Takezono, Tsukuba, Japan
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2
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Characterization of structures and properties of TiO2 powders. POWDER TECHNOL 2023. [DOI: 10.1016/j.powtec.2023.118437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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3
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Melzer JE, McLeod E. Assembly of multicomponent structures from hundreds of micron-scale building blocks using optical tweezers. MICROSYSTEMS & NANOENGINEERING 2021; 7:45. [PMID: 34567758 PMCID: PMC8433220 DOI: 10.1038/s41378-021-00272-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 03/19/2021] [Accepted: 04/15/2021] [Indexed: 06/13/2023]
Abstract
The fabrication of three-dimensional (3D) microscale structures is critical for many applications, including strong and lightweight material development, medical device fabrication, microrobotics, and photonic applications. While 3D microfabrication has seen progress over the past decades, complex multicomponent integration with small or hierarchical feature sizes is still a challenge. In this study, an optical positioning and linking (OPAL) platform based on optical tweezers is used to precisely fabricate 3D microstructures from two types of micron-scale building blocks linked by biochemical interactions. A computer-controlled interface with rapid on-the-fly automated recalibration routines maintains accuracy even after placing many building blocks. OPAL achieves a 60-nm positional accuracy by optimizing the molecular functionalization and laser power. A two-component structure consisting of 448 1-µm building blocks is assembled, representing the largest number of building blocks used to date in 3D optical tweezer microassembly. Although optical tweezers have previously been used for microfabrication, those results were generally restricted to single-material structures composed of a relatively small number of larger-sized building blocks, with little discussion of critical process parameters. It is anticipated that OPAL will enable the assembly, augmentation, and repair of microstructures composed of specialty micro/nanomaterial building blocks to be used in new photonic, microfluidic, and biomedical devices.
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Affiliation(s)
- Jeffrey E. Melzer
- Wyant College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721 USA
| | - Euan McLeod
- Wyant College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721 USA
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4
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Optimized anti-reflection core-shell microspheres for enhanced optical trapping by structured light beams. Sci Rep 2021; 11:4996. [PMID: 33654263 PMCID: PMC7925665 DOI: 10.1038/s41598-021-84665-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Accepted: 02/19/2021] [Indexed: 01/31/2023] Open
Abstract
In this paper, we study the optical trapping of anti-reflection core-shell microspheres by regular Gaussian beam and several structured beams including radially polarized Gaussian, petal, and hard-aperture-truncated circular Airy beams. We show that using an appropriate anti-reflection core-shell microsphere for the optical trapping by several structured light beams can dramatically enhance the strength of the trap compared to the trapping by the common Gaussian beam. The optimal core-shell thickness ratio that minimizes the scattering force is obtained for polystyrene-silica and anatase-amorphous titania microspheres, such that the core-shells act as anti-reflection coated microspheres. We show that the trapping strength of the anti-reflection coated microparticles trapped by the common Gaussian beam is enhanced up to 2-fold compared to that of trapped uncoated microparticles, while the trapping of anti-reflection coated microparticles, by the radially polarized beam, is strengthened up to 4-fold in comparison to that of the trapped uncoated microparticles by the Gaussian beam. Our results indicate that for anatase-amorphous titania microparticles highest trap strength is obtained by radially polarized beam, while for the polystyrene-silica microparticles, the strongest trapping is achieved by the petal beam.
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Bugaeva AY, Loukhina IV, Filippov VN, Dudkin BN. Ceramic composite [78ZrO2–21CeO2–Y2O3]/La0.85Y0.15Al11O18/Al2O3. Microstructure and properties. RUSS J GEN CHEM+ 2017. [DOI: 10.1134/s1070363217100164] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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6
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Gao D, Ding W, Nieto-Vesperinas M, Ding X, Rahman M, Zhang T, Lim C, Qiu CW. Optical manipulation from the microscale to the nanoscale: fundamentals, advances and prospects. LIGHT, SCIENCE & APPLICATIONS 2017; 6:e17039. [PMID: 30167291 PMCID: PMC6062326 DOI: 10.1038/lsa.2017.39] [Citation(s) in RCA: 166] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 02/28/2017] [Accepted: 03/07/2017] [Indexed: 05/07/2023]
Abstract
Since the invention of optical tweezers, optical manipulation has advanced significantly in scientific areas such as atomic physics, optics and biological science. Especially in the past decade, numerous optical beams and nanoscale devices have been proposed to mechanically act on nanoparticles in increasingly precise, stable and flexible ways. Both the linear and angular momenta of light can be exploited to produce optical tractor beams, tweezers and optical torque from the microscale to the nanoscale. Research on optical forces helps to reveal the nature of light-matter interactions and to resolve the fundamental aspects, which require an appropriate description of momenta and the forces on objects in matter. In this review, starting from basic theories and computational approaches, we highlight the latest optical trapping configurations and their applications in bioscience, as well as recent advances down to the nanoscale. Finally, we discuss the future prospects of nanomanipulation, which has considerable potential applications in a variety of scientific fields and everyday life.
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Affiliation(s)
- Dongliang Gao
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore
- College of Physics, Optoelectronics and Energy, Soochow University, Suzhou 215006, China
| | - Weiqiang Ding
- Department of Physics, Harbin Institute of Technology, Harbin 150001, China
| | - Manuel Nieto-Vesperinas
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, Madrid 28049, Spain
| | - Xumin Ding
- Department of Physics, Harbin Institute of Technology, Harbin 150001, China
| | - Mahdy Rahman
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore
- Department of Electrical and Computer Engineering, North South University, Dhaka 1229, Bangladesh
| | - Tianhang Zhang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456, Singapore
| | - ChweeTeck Lim
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456, Singapore
- Department of Mechanical Engineering, National University of Singapore, Singapore 117576, Singapore
| | - Cheng-Wei Qiu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456, Singapore
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, Shenzhen University, Shenzhen 518060, China
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7
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Synthesis of ZnO@Co2O3-Bi2O3-MnO core-shell structured nanoparticles for varistors applications. POWDER TECHNOL 2014. [DOI: 10.1016/j.powtec.2014.04.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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8
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Olof SN, Grieve JA, Phillips DB, Rosenkranz H, Yallop ML, Miles MJ, Patil AJ, Mann S, Carberry DM. Measuring nanoscale forces with living probes. NANO LETTERS 2012; 12:6018-23. [PMID: 23092335 DOI: 10.1021/nl303585w] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Optical trapping techniques have been used to investigate fundamental biological processes ranging from the identification of the processive mechanisms of kinesin and myosin to understanding the mechanics of DNA. To date, these investigations have relied almost exclusively on the use of isotropic probes based on colloidal microspheres. However, there are many potential advantages in utilizing more complex probe morphologies: use of multiple trapping points enables control of the interaction volume; increasing the distance between the optical trap and the sample minimizes photodamage in sensitive biological materials; and geometric anisotropy introduces the potential for asymmetric surface chemistry and multifunctional probes. Here we demonstrate that living cells of the freshwater diatom Nitzschia subacicularis Hustedt can be exploited as advanced probes for holographic optical tweezing applications. We characterize the optical and material properties associated with the high shape anisotropy of the silica frustule, examine the trapping behavior of the living algal cells, and demonstrate how the diatoms can be calibrated for use as force sensors and as force probes in the presence of rat B-cell hybridoma (11B11) cells.
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Affiliation(s)
- S N Olof
- H. H. Wills Physics Laboratory, School of Chemistry, University of Bristol, Bristol, BS8 1TL, United Kingdom
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9
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Cerbelaud M, Lestriez B, Guyomard D, Videcoq A, Ferrando R. Brownian dynamics simulations of colloidal suspensions containing polymers as precursors of composite electrodes for lithium batteries. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:10713-10724. [PMID: 22738282 DOI: 10.1021/la302135v] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Dilute aqueous suspensions of silicon nanoparticles and sodium carboxymethylcellulose salt (CMC) are studied experimentally and numerically by brownian dynamics simulations. The study focuses on the adsorption of CMC on silicon and on the aggregation state as a function of the suspension composition. To perform simulations, a coarse-grained model has first been developed for the CMC molecules. Then, this model has been applied to study numerically the behavior of suspensions of silicon and CMC. Simulation parameters have been fixed on the basis of experimental characterizations. Results of brownian dynamics simulations performed with our model are found in qualitative good agreement with experiments and allow a good description of the main features of the experimental behavior.
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Affiliation(s)
- Manuella Cerbelaud
- Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP32229, 44322 Nantes cedex 3, France.
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10
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11
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Zhao W, Yang H, Huo C. Surface nanocrystallization modification of anhydrite. Colloids Surf A Physicochem Eng Asp 2012. [DOI: 10.1016/j.colsurfa.2011.11.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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12
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Babick F, Schießl K, Stintz M. van-der-Waals interaction between two fractal aggregates. ADV POWDER TECHNOL 2011. [DOI: 10.1016/j.apt.2010.11.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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13
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Piechowiak MA, Videcoq A, Rossignol F, Pagnoux C, Carrion C, Cerbelaud M, Ferrando R. Oppositely charged model ceramic colloids: numerical predictions and experimental observations by confocal laser scanning microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:12540-7. [PMID: 20604541 DOI: 10.1021/la101027d] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Fluorescent silica and alumina-like spherical particles with almost equal sizes are synthesized. Dilute aqueous suspensions are prepared with various ratios of those colloidal particles that exhibit opposite surface charges. These suspensions undergo heteroaggregation for a wide range of compositions. The structure of the formed aggregates is analyzed by means of confocal microscopy. The experimental results are compared to those of Brownian dynamics simulations in which the interactions between colloids are modeled by the DLVO potential. Good agreement between experiments and simulations is obtained.
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Affiliation(s)
- M A Piechowiak
- SPCTS, UMR 6638, ENSCI, CNRS, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges Cedex, France
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14
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Lim JK, Majetich SA, Tilton RD. Stabilization of superparamagnetic iron oxide core-gold shell nanoparticles in high ionic strength media. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:13384-13393. [PMID: 19928938 DOI: 10.1021/la9019734] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Nanoparticles with monodisperse, spherical magnetic iron oxide cores and contiguous gold shells (Fe/Au NPs) have been synthesized in order to combine magnetophoretic responsiveness and localized surface plasmon resonance in a single nanoparticle. Such particles are sufficiently charged to be stable against flocculation in low ionic strength media, but they require surface modification to be stably dispersed in elevated ionic strength media that are appropriate for biotechnological applications. Dynamic light scattering and ultraviolet-visible spectrophotometry are used to monitor the colloidal stability of Fe/Au NPs in pH 7.4 phosphate buffered saline containing 154 mM NaCl (PBS). While uncoated particles flocculate immediately upon introduction to PBS, Fe/Au NPs with adsorbed layers of bovine serum albumin or the amphiphilic triblock copolymers Pluronic F127 and Pluronic F68 resist flocculation after more than 5 days in PBS. Adsorbed dextran allowed flocculation that was limited to the formation of small clusters, while poly(ethylene glycol) homopolymers ranging in molecular weight from 6000 to 100 000 were ineffective steric stabilizers. The effectiveness of adsorbed Pluronic copolymers as steric stabilizers was interpreted in terms of the measured adsorbed layer thickness and extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory predictions of interparticle interactions.
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Affiliation(s)
- Jit Kang Lim
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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15
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Ramanathan M, Luckarift HR, Sarsenova A, Wild JR, Ramanculov EK, Olsen EV, Simonian AL. Lysozyme-mediated formation of protein–silica nano-composites for biosensing applications. Colloids Surf B Biointerfaces 2009; 73:58-64. [DOI: 10.1016/j.colsurfb.2009.04.024] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Revised: 04/24/2009] [Accepted: 04/28/2009] [Indexed: 10/20/2022]
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16
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Rodriguez-Otazo M, Augier-Calderin A, Galaup JP, Lamère JF, Fery-Forgues S. High rotation speed of single molecular microcrystals in an optical trap with elliptically polarized light. APPLIED OPTICS 2009; 48:2720-2730. [PMID: 19424395 DOI: 10.1364/ao.48.002720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We build an experiment of optical tweezers based on the use of an inverted optical microscope for manipulating microsized single crystals, which are made of an organic dye and parallelepiped in shape. The microcrystals are directed so that their long axis is in the axial direction of the trapping beam. Their short axis follows the direction of the linear polarization of the beam. In circular or elliptic polarization, the crystals are spontaneously put in rotation with a high speed of up to 500 turns per second. It is the first time, to the best of our knowledge, that such a result is reported for particles of the size of our crystals. Another surprising result is that the rotation speed was first increased as expected by increasing the incident power, but after passing by a maximum it decreased until the complete stop of rotation, whereas the power continued growing. This evolution was not reversible. Several hypotheses are discussed to explain such behavior.
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Stott SJ, Mortimer RJ, Dann SE, Oyama M, Marken F. Electrochemical properties of core-shell TiC–TiO2nanoparticle films immobilized at ITO electrode surfaces. Phys Chem Chem Phys 2006; 8:5437-43. [PMID: 17119652 DOI: 10.1039/b610391j] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Titanium carbide (TiC) nanoparticles are readily deposited onto tin-doped indium oxide (ITO) electrodes in the form of thin porous films. The nanoparticle deposits are electrically highly conducting and electrochemically active. In aqueous media (at pH 7) and at applied potentials positive of 0.3 V vs. SCE partial anodic surface oxidation and formation (at least in part) of novel core-shell TiC-TiO2 nanoparticles is observed. Significant thermal oxidation of TiC nanoparticles by heating in air occurs at a temperature of 250 degrees C and leads first to core-shell TiC-TiO2 nanoparticles, next at ca. 350 degrees C to TiO2 (anatase), and finally at temperatures higher than 750 degrees C to TiO2 (rutile). Electrochemically and thermally partially oxidized TiC nanoparticles still remain very active and for some redox systems electrocatalytically active. Scanning and transmission electron microscopy (SEM and TEM), temperature dependent XRD, quartz crystal microbalance, and voltammetric measurements are reported. The electrocatalytic properties of the core-shell TiC-TiO2 nanoparticulate films are surveyed for the oxidation of hydroquinone, ascorbic acid, and dopamine in aqueous buffer media. In TiC-TiO2 core-shell nanoparticle films TiO2 surface reactivity can be combined with TiC conductivity.
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Affiliation(s)
- Susan J Stott
- Department of Chemistry, Loughborough University, Loughborough, Leicestershire, UK LE113TU
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18
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Lee MH, Beyer FL, Furst EM. Synthesis of monodisperse fluorescent core-shell silica particles using a modified Stöber method for imaging individual particles in dense colloidal suspensions. J Colloid Interface Sci 2005; 288:114-23. [PMID: 15927569 DOI: 10.1016/j.jcis.2005.02.073] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2004] [Revised: 02/11/2005] [Accepted: 02/18/2005] [Indexed: 11/25/2022]
Abstract
Core-shell silica particles, with a diameter of 1.5 mum, containing a dye fluorescein isothiocyanate (FITC), are synthesized by the hydrolysis and condensation of tetraethylorthosilicate (TEOS). Sodium dodecyl sulfate (SDS) is added to synthesize fluorescent core particles with the diameter of approximately 1 mum. In the addition of SDS, the surface charge reduced by counterions (Na+) of the surfactant leads to a higher degree of aggregation of the primary particles and the formation of larger secondary particles. The particle growth kinetics confirms the aggregation growth model for the synthesis of monodisperse silica particles, and also shows the dependence of final particle size on colloidal stability resulting from the addition of SDS. Light and X-ray scattering data reveal that the final particles have compactly packed structures with smooth surfaces. The seeded growth technique is then used to form a silica shell layer on the fluorescent core. The added amount of water and NH4OH has significant effects on shell formation. Finally, the final core-shell silica particles are modified by chemisorption of octadecanol at the surface to be dispersed in organic solvents. Octadecyl-coated silica particles are sterically stabilized in silica index-matching solvents such as chloroform and hexadecane to directly image separate particles using confocal microscopy. In chloroform, the organophilic silica particles disperse well, whereas in hexadecane they form a volume-filling gel structure at room temperature.
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Affiliation(s)
- Myung Han Lee
- Department of Chemical Engineering, University of Delaware, Colburn Laboratory, 150 Academy St., Newark, DE 19716, USA
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19
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Zhao L, Yu J, Cheng B. Preparation and characterization of SiO2/TiO2 composite microspheres with microporous SiO2 core/mesoporous TiO2 shell. J SOLID STATE CHEM 2005. [DOI: 10.1016/j.jssc.2005.03.024] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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20
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Bridges TE, Houlne MP, Harris JM. Spatially resolved analysis of small particles by confocal Raman microscopy: depth profiling and optical trapping. Anal Chem 2004; 76:576-84. [PMID: 14750849 DOI: 10.1021/ac034969s] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Raman microscopy is a powerful method to provide spatially resolved information about the chemical composition of materials. With confocal collection optics, the method is well suited to the analysis of small particles, either resting on a surface or optically trapped at a laser focus, where the confocal collection volume optimizes the signal from the particle. In this work, the sensitivity and spatial selectivity of detecting Raman scattering from single particles was determined as a function of particle size. An inverted confocal Raman microscope was used to acquire spectra of individual surface-bound and optically trapped polystyrene particles with sizes ranging between 200 nm and 10 microm. The particles are in contact with aqueous solution containing perchlorate ion that served as a solution-phase Raman-active probe to detect interferences from the surrounding medium. The collection volume is scanned through single particles that are attached to the surface of the coverslip, and the sensitivity and selectivity of detection are measured versus particle size. The results compare favorably with a theoretical analysis of the excitation profile and confocal collection efficiency integrated over the volumes of the spherical particles and the surrounding solution. This analysis was also applied to the detection of particles that are optically trapped and levitated above the surface of the coverslip. The results are consistent with the optical trapping of particles at or near the excitation beam focus, which optimizes excitation and selective collection of Raman scattering from the particle.
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Affiliation(s)
- Travis E Bridges
- Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, UT 84112-0850, USA
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22
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Core–shell micron-scale composites of titanium oxide and carbide formed through controlled thermal-plasma oxidation. Chem Phys Lett 2003. [DOI: 10.1016/s0009-2614(02)01760-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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23
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Houlne MP, Sjostrom CM, Uibel RH, Kleimeyer JA, Harris JM. Confocal Raman microscopy for monitoring chemical reactions on single optically trapped, solid-phase support particles. Anal Chem 2002; 74:4311-9. [PMID: 12236337 DOI: 10.1021/ac020325t] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Optical trapping of small structures is a powerful tool for the manipulation and investigation of colloidal and particulate materials. The tight focus excitation requirements of optical trapping are well suited to confocal Raman microscopy. In this work, an inverted confocal Raman microscope is developed for studies of chemical reactions on single, optically trapped particles and applied to reactions used in solid-phase peptide synthesis. Optical trapping and levitation allow a particle to be moved away from the coverslip and into solution, avoiding fluorescence interference from the coverslip. More importantly, diffusion of reagents into the particle is not inhibited by a surface, so that reaction conditions mimic those of particles dispersed in solution. Optical trapping and levitation also maintain optical alignment, since the particle is centered laterally along the optical axis and within the focal plane of the objective, where both optical forces and light collection are maximized. Hour-long observations of chemical reactions on individual, trapped silica particles are reported. Using two-dimensional least-squares analysis methods, the Raman spectra collected during the course of a reaction can be resolved into component contributions. The resolved spectra of the time-varying species can be observed, as they bind to or cleave from the particle surface.
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Affiliation(s)
- Michael P Houlne
- Department of Chemistry, University of Utah, Salt Lake City 84112-0850, USA
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